They're absolutely the community chat tool of choice these days - just about every subreddit you go to, every fandom you could ever think of, has a discord community. It's incredibly easy to put one together.
But things like Nitro seem to have minimal adoption. The game store isn't particularly compelling. They've got some partnerships with games where they offer Discord up as the actual in-game voice communication, but I haven't seen much adoption of that, and I don't know if it actually results in revenue for them, either.
It's not unique - we've seen plenty of major tech companies in similar spots - but they've basically all pivoted to advertisements as a way to make money, something that Discord has categorically said they don't want to do. I don't know what they could do to really turn things around here.