It’s a complicated question nowadays as the first generation of networks that were really all about networking have mostly died out or morphed into algorithmic feeds. So the question is whether there’s a market for this classical networking at all. If so for a network to make sense you do need networking effects of some kind as people would likely not want to pay to be registered to a service that shows them having 0 friends. I do think it’s a difficult bet.

I can however see this for niches and small groups. Something more akin to old school bulletin board forums. In a sense Metafilter works a bit that way already.