> I am saying this as a bitter outsider without a Bluesky account but with FOMO

You'll be pleased to learn that Bluesky sign-up has been open to all without invitation since last February.

> something else will come along and eat their lunch

It already happened.

Whilst Bluesy was requiring invites, Threads launched and now has the highest DAUs of all of the text social networks.

I agree with you on this, but the Threads culture of 'no bad vibes' is very hard to take

Its no longer invite only.