Gatekeeping your hobby, especially if it's niche, is 100% justifiable.

I can't tell you how many hobbies I've fallen out of love with because they've gone mainstream and changed for the worse. Magic: The Gathering is my most recent hobby I have dropped because of this, 50 percent of sets released this year or releasing aren't in universe sets, they're sets based on other IP. They basically turned the game into Fortnite. Then the in-universe sets are now full of pop culture and more modern-day technology like cars, chainsaws and freaking revolvers. Similar things are happening in Anime, video games and movie franchises which lures in new crowds that doesn't appreciate the old stuff that made those things great to begin with and will probably only be fans and consumers for a short time because they're bringing in the wrong crowd.