Some people were looking for less pozzed mod hosting sites than places like Nexus Mods. I came across this place:
I haven't gone through everything there but it does have, for example, "Hogwarts Legacy, Historically accurate 1800's Hogwarts," "WoW Wrath Classic Gender Icons," and FO4 Grounded Commonwealth.
If and when Starfield starts getting modded I am sure you can imagine what it will host.
I think something you're missing is that modders (myself included) do it for a hobby or to change something we like or dislike. I have zero interest in building a game from scratch and then going through the process of selling it. I just want to add a new weapon to Fallout or a couple spells to Skyrim for myself and anyone that's interested.
"Just build your own game!" sounds like the sams people who when they see someone do a translation patch for a 20+ year old game or build cities in minecraft immediately say that line. If they wanted to make a game they would.
But again I have zero interest in that. I don't want a "workload" period, I just want to slay a couple dragons with some sick custom magic or sword I made. And that's why I brought up translation patches. It is absolutely a lot of work but if that's how they want to spend their free time who are you or anyone in a position to judge.
It really applies to any hobbies. Would you go up to someone who likes watching football and be like "What are you doing? You could be outside practicing with a ball and make money off it!". Why would you? Dude might just want to watch football and that's the same for someone who wants to reverse engineer a game in their free time.
The problem with that is, modding is often easier than creating the code from scratch. Adjusting code and then troubleshooting what it breaks is leagues simpler than actually doing it.
Not to discredit the skills and great shit they are able to put out, but you'd likely filter out 99% of mod creators immediately by asking for original creation over modification.