First, the cultural base for classical music, and the arts in general, has been eroded by bad TV, bad radio, and bad education. No amount of government funding would fix that -- the only answer is for people to want to have good taste.
Second, you're right about the effects of the big stations. Most of them play the same schlock, in pretty much the same order. The problem in that case is that the radio corporations are big (i.e., they have no feel for local wants or needs), and they're in bed with the record companies (which means that they get paid to play crap).
As with so many other problems, the dearth of good radio can be traced to a populace that doesn't know any better.
But look how many public radio stations play essentially the same few programs, just like the commercial stations.
I'll give you another reason for the ending of "classical" programming, political correctness. At least on Pacifica you will hear honesty about such decisions "they are dead white European males".