Hard agree. Gatekeeping is a good thing. It is how you ensure that people who join a group are actually a good fit for the group. For example, if someone wants to join a D&D group but doesn't like that the game is a dungeon crawl where you just go kick monster ass without a pretense of story, nobody will be served by the group deciding to try to adjust to welcome the new person despite that bad fit. Not only the existing group, but the prospective new member, will be better off if they each go their separate ways and play the type of game each enjoys.

It's good to not exclude people for arbitrary reasons (though even this requires the caveat that one man's "arbitrary" is another man's "important part of our identity"). But we also need to recognize that it's ok for something to not be everyone's cup of tea. There isn't some kind of moral mandate that everything must be maximally welcoming to all. Unfortunately, we don't recognize that in our current culture, and in fact we stigmatize it as "gatekeeping" which is deemed to be toxic. But the culture is wrong about this.