I believe, due to the format of engagement, its easy to spend a lot of time there scrolling - so consider
(1) only using the platform on your desktop computer, instead of phone,
(2) limiting time - 25 minutes a day is enough!
(3) Mute spammers, complainers, people with negative attiudes - you can't catch them all, but you can intentionally shape your experience over time.
(4) Subscribe to tags of your passions (example: #piano, #makerspace, #drawing, #cats, #jujitsu, #cncrouter, #3dprinting), and try to lean into that instead of getting caught up in endless political reactions - which never ends. You can be intentional, and subscribe to people who have a positive vision for the version of the future you prefer.
I certainly don't need a billion users. I think I'd be happy with 100,000 users -- what is your number?
I think this is related to the question of how big of a city do you need to live in before you can find something to do and are not bored living there. I'm fine with a city of, say, 50,000-100,000. That is more than sufficient for me to find an appropriate number of likeminded friends and neighbors as well as interesting pursuits.
I don't think that's a meaningful parameter to think about? I'd say that on any social network, I have meaningful, ongoing relationship with maybe 20 people. I suspect that's the norm. But that doesn't mean you can join a social network with 20 users and get that. I mean, if it's a mailing list for friends and family, sure. But not if it's 20 randomly-selected strangers from around the world.
So the critical mass to make the "random stranger" type of a social network work is much, much higher than the number of daily interactions you need to keep coming back.
By the way, if your number is not the same as mine, I am not intimating that this makes you deficient in some way. Everyone has their own number.
Bluesky and Mastodon users can interact with each other (provided both parties opt in). I'm on Mastodon, but I see my friend's messages (he's on BlueSky) and vice versa. My replies show on up on BlueSky and vice versa.
I don’t see why it is “zero” sum, nothing stops you from posting to more than one social. I mean, I have relatives on Facebook and no prospect for getting them to change so I cut-n-paste what I posted on Mastodon to Facebook, Bluesky, LinkedIn, Tumblr, and all sorts of places.