Studios like Fromsoft are known for recycling assets to a very noticeable degree. It‘s just part of the game and another reason why AI makes so little sense in the creative world. Studios already have their asset libraries. They don‘t need to prompt something that already exists because they already have it. What they need are new ideas and AI is terrible at delivering that.

I don't disagree with your main point, but I think the Mario sprite thing is just as easily explained by technical limitations as artistic ones.

You see it in every EA game, but they also reuse the gameplay itself.