Agreed. Modding doesn't "fix" Skyrim either. It adds surface-level content and tweaks but the fundamental bones of the game are still there and they are heavily flawed. One of the few exceptions I can think of are things like Skywind but that's only because it removes Skyrim's story entirely, overhauls many of its mechanics, and uses the world/lore/story of one of Bethesda's better games.

And in the case of Starfield - it's entirely beyond salvaging with mods. Mods will not be able to fix the biggest problems with that game because they are literally the very way the game was made. To fix them would require basically remaking the entire game from scratch.