Final fansty isn’t that kind of ip. Different ones are set in different universes/planets, with different casts. There’s a billion different things you can explore. One game is basically medieval, another is basically cyberpunk. The things you explore are completely different and the only similarities are the name of the ip, the names of the gods, and maybe the names of some of the characters.
There aren’t many games you can make that argument with because of the way technology has advanced so much.
Elder scrolls v skyrim was easily the most successful, but your suggestion is stopping at morrowind which is an entirely different game. Tomb raider today is a different game from when it came out. Some ways for the best some ways for the worse. But there are always new things to explore. Even if it’s just mechanically.
Sure you can make that argument over something like the yearly sports games. But these games are not yearly releases.
Mods are a different beast and not representative of the game, devs, or player base. Mods like this often get removed from big modding sites like Nexus, forcing them to be mostly in their own spaces. (There is/was a bg3 mod overhaul that makes every black npc white, some lesbian npcs into men so they are straight couples, the ability to change your gender and lock it to the body types. Etc and so on. But you can’t find it on Nexus. I remember the white Wyll mod but it got removed within 3 days)
It’s another matter entirely when a developer bakes this kind of shit into the game. Not every game has mod support and not everyone mods.