It depends. The vast majority of what you call the "air product" is either music or commercials. If the music is mediocre, that's not radio's fault. People like what they like, and if it's your job to introduce mediocre music, then there's not much you can do. My question to you is if radio hired actual entertainers to host radio shows, would that make more money? Having entertainers on the air would mean they'd likely play less music. Is that what people want from radio?
To your broader point, most companies (not just radio) are run by salesmen, accountants, or lawyers. How much imagination do you expect from accountants or lawyers? But they're the only ones willing to deal with the regulations required to own radio stations. You talk to a typical DJ and he/she has no idea how to run a company, file regulatory paperwork, or sell spots to advertisers. They grow beards, wear jeans and t-shirts to work, and live in rental apartments. Would you work for someone like that? I want someone who will make sure I get paid, make sure I get health insurance, and deal with all the crap I don't want to deal with. Me, me, me. So that's what brings us to where we are.
However, it wouldn't take a lot for a group of DJs to pool their money (what little they have) and buy radio stations. It happens. But most DJs don't think that way. They just want to get paid a regular salary with benefits and play golf.