The more popular a community becomes, the shittier it gets. The easier you make it to join and interact with, the more popular it will become.
In the case of places like Gab, Truth Social, Parlor, and other right wing nut job havens, while the quality of users might not get higher if you raised the barrier to entry, those places certainly wouldn’t have become as popular as they have.
But the barrier to entry isn’t the only reason they’ve congregated there, they have other cultural reasons driving them, primarily the owners or moderators being friendly to that kind of mindset. I don’t think the same crowd would be able to gather here as they’d just get defederated.