I assure you you don't need invites for everything. Not sure if you read the whole article, but there are plenty of links that provide groups to join. At least you tried it though. Sorry to hear it's not your thing.
I read the whole article. There are only two links: one is to the news letter, one is to a 5 minute tutorial on how to setup a server aka planet.
Well, there's also a link to imperceptible.city that you have to pay for. I mean, of course I'll gladly pay for something that promises "a network of thinkers, scholars, writers, founders, and sophisticated creators". Haha, no.