Bioware did it tho. As did Obsidian.
They gave us a full 1-20 adventure, then raised the level caps to 40 (in nwn) and 30 (nwn2) in expansions. 3.5 had epic rules that supported higher levels.
Aren't level 20s like gods or something?
Not even close. Incredibly powerful, but far from gods, demi gods or other powerful beings.
An avatar of a god is around CR 30, which would need a group of level 17-20 adventurers to defeat unless they have some sort of plot protections like in the rise of Tiamat.
If we go into combat in BG3 with anything near the power of an avatar, we would 100% need to be near level 20 to do so (unless they have some plot device to stop us getting stomped)