>>53514405because as a teenager it's pretty probable you're gonna reject stuff you used to enjoy as a younger kid because you want to convince yourself you've grown up.
so if you enjoyed pokemon as a kid then you're gonna try to nitpick pokemon details like "OMG HE'S FOREVER 10" or shit like that. if you still enjoy pokemon as a teenager you're gonna try to do it in a more "serious" way even.
when you grow up again and become an adult these emotional barriers tend to drop and you're gonna end up realizing you still enjoyed this stuff all along, bullshit and all. which is why you're getting nostalgia bombed by ash ending his run.
tl;dr as a kid you loved it, you grew up and hated it and then you grew up again and remembered you loved it.