A few other smaller subcultures have gotten a foothold on Mastodon; it's far from a ghost town. Another upshot is that unlike anything else you listed, it's decentralized and federated, so your instance could never be taken down.
Nobody (except a small minority even among techies/geeks/nerds) really want to go through the hassle of joining yet another platform.
Does not matter if it is free, has better quality, finer controls, is federated or not, moderated or not.
I managed, years ago, to convince a decent number of people to follow me on Google+, but the sad reality that now it's either Facebook (which I never created a profile for) or "don't call us, we'll call you...".
I proposed it as a per-pay feature to MeWe but so far I only got a canned "thanks for your suggestion" - my main problem is that even what they call "Pages", like the BBC MeWe page is visible only inside the app itself.
What I would like to see is some general, decentralised standard in the style of email and usenet, where everybody has their own identity they can use to post and respond, and block content from trolls and spammers without them easily circumventing that block (well, that clearly doesn't work with email, but spam filters do a decent job).
This helps a bit when you are, for example, deciding if you want to invite them to join your group, or have received a request from them to connect or stuff like that: before that you had only the masthead pic and their nick to decide (as most people do not even bother to fill in their profile).
But [I did test it myself] when you try to copy the url of your MeWe profile or a link to a specific post of yours and open it in a different browser you will be asked to login to MeWe.
"Pages", as I said, despite being designed for special entities like fan clubs, newsagencies and so on, behave the same way: outside of MeWe you cannot access them. They are cheap though (like 3$/month) so my suggestion to MeWe was something like:
"Please allow me to be able to make Public posts available to non-MeWe members. I will be glad to pay for this a monthly fee in the ballpark of what you ask for Pages, and it would be ok if - in case I stop paying - all my Public post revert to the current behaviour (and become visible again outside in case I start paying again)".
Looked reasonable to me, and I understand they are looking for ways to monetize some of the services... except that at the moment you can pay for stuff like "an extra set of emoticons/avatars" or "Activate Night Mode"... :-/