Nothing mythical about mesh networks.
https://en.wikipedia.org/wiki/Guifi.net
to name a few.
And there's nothing mythical about the other two things you mentoined either, just look around the protocol you're using right now. Existence proofs abound.
Discussion
Those a wireless networks. But are they "mesh", other than the name? Can I see a map of the topology? Melbourne had one like that once: https://www.melbournewireless.org.au/ It mostly worked by one guy installing an antenna on thebl roof of a skyscraper and everyone pointing theirs at that. 🤣
they have 2370 nodes (and yes, a few "supernodes" like you're describing). the topology is good. it is absolutely a mesh in more than name.
When hurricaine Sandy hit new york, some neighborhoods were completely cut off and only had their mesh peers - which was able to provide important local connectivity to those people.
This looks somewhat promising. The supernodes are worrying ofc. Real mesh networks usually exhibit more of a small-world topology. https://en.m.wikipedia.org/wiki/Small-world_network