IWhat makes RADIO is the local personalities. Local news, local information. Local advertising and sometimes local music. You see, for the homesick former resident or just anyone randomly looking for what life sounds like elsewhere, 24/7 locality says something. It means you're in the air there, aware and everywhere.
No, what makes radio is entertainment or information.
A national format can provide most of the entertainment better than a local one can. That is why the personality and panel shows on TV are national, not local, going back to Steve Allen.
Our current technology can provide all the national content, and integrate it with a mix of local and national ads, local weather and other service elements and even a localized playlist. But it can be run without a local staff or studio and a parallel national service can be streamed... or the web service can detect your location and provide the local station when appropriate. Seamless on a smart car console, a phone or by asking Alexa. And, if you still have a radio, you can get it there.
Only big national formats can compete with the giants going into streaming. And by providing localization on the local signals and regional customization on the streams, the owner can sell national and local at the same time. And radio groups have staff on the ground in lots of markets to do this already. Townsquare is even doing it in markets where they have no stations.
Trying to make the old model work forever is not going to be an endgame. Of course, there will be room for some local services, particularly in smaller markets, but they will likely integrate that service with a national format service.