So I know people have been lamenting the woke RPGs that infest the industry constantly and that's understandable. Something I've been researching as you well know is RTS mechanics which as it turns are also very similar to CRPG mechanics in particular with the selection box and so on, RPGs seem to be smaller in scale and more story based. I've also been looking up some pretty good tutorials on slightly more complex stuff like skill trees and proper drag and drop inventory.
Here's how I would do an RPG or CRPG modern style, you should be able to adapt to any RPG you want whether it's party based or not.
Use the dialogue addon I've referenced earlier because it will save you a crap ton of time and is very versatile. since it's already their why reinvent the wheel? You can also add character avatars to the dialogue among other things.
https://godotengine.org/asset-library/asset/1432
https://www.youtube.com/watch?v=UhPFk8FSbd8
I would also have a look at this youtube tutorial on RTS selection, why? The selection box mechanics will work just fine for a party based RPG. I went out of my way to update this code the guy provided and make it work for Godot 4 so don't worry about having to implement it yourself.
https://www.youtube.com/watch?v=JFQXI3to0b4&t=113s
https://github.com/1Lethn1/Bean-Commander-3D/blob/main/3DSelection
Came across a very interesting video on skill trees, so if you want to make a classic talent tree system or something else you absolutely can.
https://www.youtube.com/watch?v=1uODBjnTtG0
Finally inventory, even though I prefer lists purely for the sake of simplicity and ease of implementation I think I might force myself to go through a tutorial sometime simply to understand all the mechanics behind drag and drop. I may end up liking the drag and drop mechanics enough though, depends on the type of game. I am a sucker for clicky buttons that are well designed.
All you need to make a good RPG is four pages out of Dark Heresy v1. Specifically, the critical effects tables. Like, that's literally all you need. Dig this:
Critical Energy Effects - Head:
7: In a gruesome display, the flesh is burned from the target's head, exposing charred bone and muscle underneath. The target is blinded permanently and takes 1d10 levels of fatigue. Also, roll 1d10. This is the target's new fellowship, unless their fellowship was already 10 or less, in which case nobody really notices the difference.
9: Superheated by the attack, the target's brain explodes, tearing apart his skull and sending flaming chunks of meat flying at those nearby. The target is no more.
10+: As above, except the target's entire body catches fire and runs off headless 2d10 meters in a random direction (use the scatter diagram on page 196). Anything flammable it passes, including characters, must make an agility test or catch fire (see special damage).
Warhammer 40k TTRPG critical damage tables always live rent-free in my head.
The best ones are the plasma-related ones.