It only ever works if you have a 100% bulletproof method of detecting "fakers" from the "genuine ones", which, considering the nature of human psychology, is fundamentally impossible.

So okay, fine, let's say you get a community to agree to filter out perceived "fakers" from your spaces. What happens then? Well, off the top of my head, I can easily see a hierarchy form based on who embodies what the space is made for the most, which leads to constant purity testing, and paranoia. People who may be that thing, but don't realize it would be scared off, or shamed from ever exploring that part of themselves, that is guaranteed psychic damage, and a lot of energy that could have gone towards helping others in the space cope and thrive, had instead been spent being an identity cop. And since ACAB, that makes you not just a bastard, but an abusive bastard.

So you may ask, 'what is the alternative, we just accept everyone, including the "fakers"'? To that i say, "What are you losing, really?"

So what are the consequences of refusing to gatekeep? Well, those who come in the spaces not as a person who embodies the thing the space is for will have one of two outcomes. Either they find out they are of the thing, in which case it's a net positive, because self-discovery is always a good thing. The other scenario is that they realize that they do not fit, and leave, this is also a good outcome, because the person in question would have come out with a deeper understanding of the thing, and why they are not it, which can also help them figure out other aspects of themselves.

In practice, external ingratiation into vulnerable communities is impossible, because the amount of emotional labour involved in participating in those spaces are huge, and it's easy to see even the best of masks slip from the faces of those with less than honest intent. (And even then, antagonistic figures may very well also be a member of the vulnerable groups, and are struggling internally to come to terms with it)