IMO this can be neatly solved with a peer-to-peer market based system similar to Helium https://www.helium.com/mobile.

(I know that helium's original IoT network mostly failed due to lack of pmf, but idk about their 5G stuff)

Network providers get paid for the bandwidth that flows over their nodes, but the protocol also allows for economically incentivizing network expansion and punishing congestion with subsidization / taxing.

You can unify everyone under the same "network", but the infrastructure providers running it are diverse and in competition.