There a many huge mesh networks all over the world, just not so many in this country. Guifi in Spain has 29,208 active nodes so there is no argument that mesh doesn't scale. https://guifi.net/en/node/38392
I can't find much in the way of specific technical information in English, but from what I can tell Guifi has are tiers of nodes, ordinary nodes and supernodes, where nodes connect only to supernodes and the supernodes have fixed, manually configured directional radio links to other supernodes. It's a lot easier to get thirty thousand nodes on a mesh network if the vast majority of them aren't actually taking part in the meshing and the ones that are use fixed infrastructure links. It basically avoids all the inconvenient "mesh" part.