Is this a cult?
It's definitely not a cult.
Why isn't this a cult?
Attributes of a typical cult are authoritarian control, extremist beliefs, isolation from society, and veneration of a single individual. We have very little self-control, we don't believe much of anything, we like to go to concerts and talk to people, and there's nobody really in charge.
How do I join this group that's definitely not a cult?
You can't. This was a thing that more or less spontaneously happened during the weird lockdown of 2020 that nobody really wants to do again. Maybe we will open it up again during the next pandemic.
Isn't "It's definitely not a cult" just the sort of thing a member of a cult would say?
Well, you got me there...