I would not call that one "stone age". It is just the only VPN type which allows a decent P2MP operation. And the topology is a complete mesh. And the mesh concept is actually more modern than you think: see WDS networks, redundant links between AS, backup links between providers, internet of things... Stone age was the classic architecture, with backbone routers, mesh IS the future.
The basic idea in a mesh is redundancy, and no single point of failure. And a complete mesh actually has no point of failures execept the nodes themselves. Our biggest problem is actualy the fact that we have a single encap information provider, the last element which is NOT in the mesh.
And the biggest issue is exactly what you say: "which only need a router of backbone". One single router, one single backbone, one single device, centralized costs.
Who pays for the equipment, who hosts and maintains it, and who ensures the bandwidth for all the 44net traffic to pass through it? In a mesh, each user has to ensure only his own bandwidth needs, on a on demand base.
So IMHO, this network is actually extremely modern. It was out of its time 20 years ago, and slowly enters mainstream now. Actually the mainstream alligns to our network...
73s de Marius, YO2LOJ