Nostalgia worship

You're raised with something, and suddenly, everything that enters your life afterwards is considered shit. Nostalgia worship is the worst:

When I was writing my super long "Bright Eyes"-article, I came across a guy saying that the movie Watership Down was better than most what Disney had ever done.

Holy balls. That's a very serious claim. A seriously delusional claim.
But that's what happens when something is part of a huge crowd's past, and was considered the underdog for a long time. People need to remind themselves that being an underdog should not earn something special points and doesn't make it better than whatever similar piece of media happened to gain more popularity. Popular things are sometimes popular because they are "good", you know.

Watership Down is not better than most Disney movies.

The music of today is not worse than the music of the past.

People are not more violent compared to the old days.

Things always keep changing, and there are no rules because of it. We're all sorry you're not a child anymore, but whatever happened to be going on in that time period is not better than what is going on right now.
The cartoons, songs, and people of today are going to be nostalgic to the generations of today. It's their childhood. Who are you to bash it.