The biggest thing to keep in mind when "gatekeeping" is that it's more important to step up and take on the role of a "initiator" or "sponsor" into the culture, and pass on the community knowledge that makes the culture a special place.
Of course assimilating the new people would be the best outcome. Sadly I have ran into enough that go in with the intention of changing the subculture that I am now VERY skeptical of any new person.
But then we can't look down on the new people and complain about how their fun is ruining our fun /s.
If they come in with plans to change the subculture...