I'd pay $5-ish per month for social media if it came with no ads or data harvesting - just a more privately scoped version of Facebook with some of the useful bits like event scheduling and discussion groups. Of course the problem is getting non-technical people to value their attention and privacy at more than $5/month in order to catalyse the network effects.
This has been tried though, app.net came and went. I mean if you want those things they exist in some form with Mastodon, Matrix/Element (not sure about the event scheduling).
Note that I specify provider above. Twitter is somewhat useful, but that is despite of, not because of the interaction design of it.
Edit: IIRC app.net was a bit overpriced and had some weird limitations too, although the latter might just be me remembering that they copied all the design mistakes of Twitter for no good reason.
Edit2: If anyone is in doubt at all: Twitter is popular because of the network effect. Everything else has been solved better by one or more competitors.