This is a bit longer than what the above wrote.

Part of the problem is Eren seeing the future creates a predestination paradox because of how the writer decided to use the future memories ability of the Attack Titan. In addition to it being the only one that can defy the progenitor parasite thing it can share memories with its other users, back and forwards in time.

This first gets hinted at in flashbacks when Eren sees his father talking to the previous user who mentioned Mikasa and Armin despite neither being born at the time because he was unintentionally being sent Eren's memories who was still brand new to the whole thing. That alone is enough to show future users can influence past ones despite it all being a closed loop/predestination paradox, which is later explicitly shown when it turns out that while Eren's father was intending to go and kill the Founding Titan user and take that power, he stops before actually doing it because he can't bring himself to actually kill the guy and his family who are also present. Until Eren projects himself and his brother directly into their father's memory and Eren talks him into doing it. It's at this point the Attack Titan's ability to defy the Founding Titan/progenitor is revealed (1) because both the Founding Titan user and his family don't feel threatened in the slightest at first since no other titan can go against the Founding Titan or it's commands. The realisation comes too late however and after being talked into going through with the attack Eren's father kills everyone and takes the Founding Titan power which later is passed to Eren.

All of this leads back to the problem of there being almost no way to stop the whole titan cycle because 1) a previous Founding Titan user imposes a pacifist rule on everyone (2) else to not use the Founding Titan power to unleash the Colossal Titans (3) that were in the wall, and 2) the progenitor is basically God which knows and controls everything titan related with a very slim exception which is what leads to its eventual death. This is why only the Attack Titan can be the one to stop it however in order to use that ability in the first place it needs a direct bloodline back to the husband (9) of the first user, Ymir, who found the progenitor parasite and those individuals number in the single digits. Eren's brother Zeke is one of them. Zeke's mother was another and eventually became the Grinning Titan that killed Eren's mother at the start of the series - something that is later revealed to have been done under Eren's orders of all things so that Bertold wouldn't be killed instead as he had a part to play years later. Historia is another, and it's when Eren touches her hand he gets the vision of the future due to the physical connection made with someone of Royal blood (4). This effect is first seen when Eren makes physical contact with the Grinning Titan and ends up commanding all the other titans in the local area to tear it apart, showcasing Eren's first use of the Founding Titan's power.

However this only works if the person with royal blood is also a titan and therefore has whatever spiritual/magical connection exists between them and the progenitor/Ymir. Zeke has the Beast Titan power so that means he could potentially work with Eren to unleash the wall titans, however Zeke has his own plan (5) to use the Founding Titan power to sterilise everyone that can ever become a titan in order to remove titans from the world without conflict. The biggest problem with the whole thing is that both sides need to agree on what is going to be done, so Eren can't use the bloodline ability without Zeke letting him, and Zeke can't use the Founding Titan power unless Eren lets him. Or that was the assumption since when the two finally do attempt it the progenitor (6) sides with Eren and unleashes the wall titans which Zeke gets dragged along with having been overruled by God in effect.

Eren then wipes out most of humanity as mentioned, the Survey Corps meet back up with Reiner/the Armoured Titan and his team who have several of the other named Titans, Jaw/birb, Cart, Annie/the Female Titan who finally wakes up because Eren freeing the wall titans also breaks her crystal prison, and they all try to stop Eren. It boils down to the named titans fighting not only previous named titan users who Eren briefly resurrects/creates simulacrums of for drama/fighting, but also then everyone else left alive after the progenitor is exposed and releases a gas which transforms people into titans. While everyone is dealing with that and trying not to kill their friends under the control of the progenitor, Mikasa and Levi go after Eren because it's revealed the only ones other than the Attack Titan who can defy the progenitor are those of the Ackerman bloodline who were humans experimented on and given pseudo-titan abilities (7). That's why they're so dangerous to everyone else and it lets Mikasa eventually get close enough to kill Eren for good without the Founding Titan or progenitor stopping them. Which is how Eren knows it will eventually play out if and when he goes about destroying the world, hence the "suicide by cop" play with Mikasa.

It's extremely convoluted, mostly because of the predestination paradox as time travel is always a mess in stories and even more so when it's a closed loop where things only ever happen because they happened and caused someone to make them happen which is a recurring point in AoT by the end.

Grisha only kills the Founding Titan user because Future!Eren talks him into it by bringing up Grisha's little sister who was murdered by guards and killed by their dogs. (8)

Eren's mother is killed because Future!Eren commands the Grinning Titan to kill her.

Eren unleashes the wall titans because he sees the future where Future!Eren unleashes the wall titans.

All in all the series just ends up as gore porn where good and bad characters get killed in horrible ways and some of the best characters suffer meaningless deaths, rip Sasha the potato girl, while some of the worst survive and continually piss off the readers over and over and over and over and over. Looking at you Gabi.

Edit: Adding a few other notes to explain some things a bit more.

(1) This also revealed to Zeke that his father wasn't the terrible person he thought his whole life. In fact because of how the memory projection works he's able to actually talk with Grisha despite having been dead for several years and last seeing Zeke even longer than that.

(2) This is done because the very first titan user Ymir, who is basically a "Mitochondrial Eve" for every single person who can become a titan which is almost everyone on Paradis Island and those living in the ghetto on the mainland, is entirely subservient to the royal bloodline as she was married by one of the royal ancestors who treated her as property and breeding stock resulting in 3 daughters that later spawn the rest of the sub-race which can become titans. The girl was young, naive, and had no actual understanding of the world or the fact she was the singular most powerful thing on the planet because she always did as she was told/ordered by the King. This subservience persists centuries after both have died through those with the royal bloodline ordering her as the Founding Titan to do various things.

(3) Unleashing the Colossal Titans is the only defense the people living on the island of Paradis have and it functions as a nuclear deterrent more than anything. "If you attack us we will unleash the titans" is the whole play and is entirely retaliatory in addition to later being proven as never going to happen anyway because of the Founding Titan ensuring nobody could even do it.

(4) This doesn't go against the "must be a titan" rule mentioned since it's really just Eren using his own power to look forward at his own memories for the first time rather than using the Founding Titan power again, however there might be enough syncronising with Historia as a direct descendant of

(5) Exactly how much of the mass sterilisation plan is Zeke's can be debated since it's first prompted by the previous Beast Titan user that Zeke eventually kills and consumes to become the next one. It is repeatedly shown that users inherent not just the titan power someone has but also their memories. Eren gains his father's memories and those of previous Attack Titan users. Zeke gains the memories of the previous Beast Titan. Reiner will have gained the memories of the previous Armoured Titan. Bertold will have gained the memories of the previous Colossal Titan. Annie will have gained the memories of the previous Female Titan. Ymir [not the progenitor but someone else with the same name] gains the memories of the previous Jaw Titan. The royal bloodline retains the memories of past Founding Titan users by ensuring it's only ever passed on to a direct blood relative, and so on. Were any of those to be killed and consumed by another titan their power and memories would pass to that titan, and this happens several times with some of the named titans which is later brought up just how much of certain actions afterwards are entirely their own or influenced in certain ways. The most highlighted being that after Armin kills Bertold and becomes the next Colossal Titan he spends a lot of time visiting Annie who is trapped in her crystal prison and Bertold previously spent a lot of time fawning over Annie, so are Armin's actions his own or Bertold's, or a mix of the two?

(6) Just to clarify this bit about "the progenitor sides with [Eren]" it's Ymir herself who sides with Eren and not the parasite. Zeke as one of the royal bloodline tries to command Ymir to obey him however Eren argues he can finally free her from serving the royal bloodline despite Zeke's plan having a similar end result.

(7) Something I should have brought up originally, the Ackerman bloodline is entirely immune to becoming a titan because of the experiments, it's why the gas doesn't affect them. This puts them somewhere between the two sub-races of humanity which are the baseline humans, often called Marleyans, and those able to turn into titans if affected by certain things such as the gas or an injection of titan CSF, often called Eldians or "Subjects of Ymir". To call the Eldians an analog for Jews would be an incredible easy step since they are not only limited to set ghettos on the mainland but also literally wear yellow star armbands.

(8) Eren talks his father into going through with something Eren only knows happens because it happened already.

Edit 2:

(9) I posted this wrong originally suggesting Ymir was the source of the royal bloodline when in fact it that of the Fritz/Reiss family. The Fritz bloodline stems from Ymir's husband and the father of her 3 children, with the Reiss bloodline was a later Fritz branch family that Manga are so often fond of. How exactly the Fritz/Reiss lines stayed distinct enough when all potential titans can be traced back to Ymir and her 3 daughters doesn't make sense since both lines are still related in some distant way to every other Eldian anyway. But then that's part of the overall issue with Attack on Titan that it doesn't do well under scrutiny the longer time passes.