It’s called “environmental amnesia” and it’s an actual issue environmentalists discuss how to combat. The climate crisis makes it more widespread but it’s been something that’s happening for generations. The story of The Lorax describes it beautifully. The idea that what you remember is what you consider normal, but if the changes happen slowly over generations, you don’t see how large they are because you don’t personally remember them being very different, even if you were told stories about it.