Part of the issue is that an awful lot of people acted like they thought they owned Twitter, and when Twitter changed out from under them they flocked over here, decided they owned this platform, and started making demands that everyone behave the way they wanted them to.
When you say the welcoming culture needs some work, that group of people is happy to be unwelcoming to those they don't want on "their" platform. If you don't share their vision for the platform, they don't want you here anyway.
My point in saying this is sort of understanding what we're working with.
You can admonish those people for being unwelcoming, but they'll just say, "Good."