Well obviously some people would pay. The hurdle that a company needs to clear is getting enough people to pay to support both an engineering staff and the infrastructure costs.
Do the math on how many people are necessary to run a web site with on-call rotation, minimum moderation, and someone to run the business. The number of $2/month subscription required to make that work is prohbitively high.
> but perhaps lots of smaller, focused social networks at $2/pop could work
Even large, free, well-funded social networks are failing to get significant traction or running into echo chamber problems (Bluesky).
I've been hearing for years that a paid social network would work, but if the unpaid social network competitors can't get any traction, what makes you think adding a $2/month signup hurdle would improve the situation?
If you want to see a real-world example of people squirming out of their claims that they'd pay for ad-free services, take a look at any HN thread discussing YouTube premium or their ad-block evasion efforts. The price for ad-free YouTube is reasonable for as much as people watch it, yet when cornered the same audiences who claimed they'd pay for an ad-free version suddenly come up with a multitude of new excuses for why they're refusing to pay. My personal favorite claim (which invariably surfaces in every thread) is when people say they would happily pay for YouTube premium if they weren't so aggressive about adblockers.