Why doesn't Matrix just call "spaces" servers? By calling them spaces, they have created a learning curve for no reason.
Even just saying you have to download a client called Element to access Matrix is not intuitive. To access Discord, you download a client called Discord.
I just signed up and tried to figure out how to join any remotely interesting community. There were none.
There were a bunch of public communities - not many - and I think the most interesting ones in the public room list were either Element Android, Telegram, and Rust. And Rust is one of my most hated games that I wish I'd refunded.