I am in 26 discord servers total. Out of those, only four are for things outside the Steem ecosystem, but they are all crypto-related.
Out of the remaining 22, I would say 10 of them are official Steem project servers or large communities. I am not really super active in any of them. There are a few dead ones as well that I like to keep around because I am a hoarder I guess? They get dragged to the bottom of the list.
I don't use steem.chat much these days, even though it is where I met a lot of my people; it is just so unusable on mobile which is where I spend a lot of my time now. I'm not on Slack, and I was on Telegram for a while but I couldn't handle the incessant spam anymore. Discord is pretty much the place.