I came into this thread to say exactly this. I don't run online, I'm a strictly in person sorts person (or over zoom with close friends during recent quarantimes) But if I was collecting a group online from any source at all and I didn't feel some of the people were a good fit? I don't know how committed I would be to explaining that to them. I would like to think that I would have an adult conversation with them about it because I'm a 43-year-old man not a child, but I've also never been in a spot like that so I can't say for sure. I might just ghost because I don't know if I owe strangers anything.
It sucks to feel ghosted or rejected though. So I can understand OP's frustration.
Still, I don't know if an entire community needs to take individuals to task. Reddit isn't real life, not even close.