This line of reasoning implicitly treats those products as some sort of public good. I imagine it’s beneficial to their owners—but is it to the users?
There’s a conflict of interest here. Networks want to be free. Huge account numbers and de-facto public good status positively influence network valuations and allow them to charge more for ads; armies of troll and no-value accounts greatly inflate the numbers; the loser turns out to be legitimate users. If we are sure they remain afloat if we pay them, why should we worry about product’s popularity more than our own treatment?
They are not central parks or public squares. They don’t have the obligation of being free. They are free to discriminate subscription prices between countries, which many companies do today (Apple Music is 5 times cheaper in India than in the US[0]).
And if geographical price discrimination is not enough, if I’m poor I have the freedom to use another social network that charges less or nothing; when I (hopefully) grow my income and get fed up with myself being a product of X I can choose to invest into a more expensive tier of social networking and move my social presence[1] to Y—what’s wrong with that?
I suspect that normalizing paid options could make social networking more heterogenous, encourage competition, and likely benefit the society in the long run.
[0] https://www.cashnetusa.com/blog/which-countries-pay-most-and...
[1] If https://datatransferproject.dev pans out, I could perhaps even take my posts with me.