Discord often solves this by showing an alert when you login. Product updates and other news often shows up there. You have to close it to get into the app.
The mindset around account recovery would be: if you value your information in your account, add an email. Otherwise, you can start again if you lose it. Doesn't work in all situations.
You're right. Even I underestimated the impact of the one click to join.
I don't remember the last time I joined a community or Slack where I had to enter a bunch of info, but I see in my Discord a bunch of servers I've joined because it is so easy.
I agree. The core reason to switch for me (and I assume many others) was because the core features were better than competitors and it was free.
On exposure outside main demographic: servers that are gaming adjacent like anime, content creators, and programming already see large numbers of members. A promising sign.