When the OP article was posted in 2021, Zulip didn't even have public access as an option. This basically would make it a non-starter for what the article author suggests it for, as that's worse (having to make an account everywhere) than Discord, Matrix or IRC.

To be honest I don't have too much experience with Zulip or Rocket or all of these other new platforms, but my current default assumption is that they will always be designed foremost for organizations rather than the "I am in 20 communities I am somewhat active in[1]" like Discord. Matrix always seems like the better choice here... but it's got its own issues.

I also don't put much regard into the author's word here because unironically suggesting IRC in 2021 means they're off their rocker.

[1] I know you can only join like 100 servers without nitro ok.