The bumps are just a symptom of thinking that is out of touch with the target audience.
It depends on what you think the target audience is. Some think it's boomers 65+. That may be, but it's primarily on AM radio. At some point, talk has to reinvent itself for FM, and music can play a part in reinventing talk radio for younger demos.
The mistake talk radio has made is forgetting it's supposed to be entertainment. Rush knew this and used bumper music as a form of imaging. Fox News did the same thing in it's early days. Now the best examples for the use of music in talk is on ESPN. They have libraries of topical popular music that they use to punctuate their stories. That makes what they do more entertaining than just having some guy blabbing non-stop.
Of course, one of the problems of using popular songs is that the most topical music today is rap, and talk show hosts and the boomer audience hate rap music. But if you want music that reflects what people in the demo are talking about, it helps to know rap music. That might mean hiring someone who's under 50 to produce the show, since the host is likely too old. But that's also part of the problem. People wonder why the audience is aging, and it's because most of the people on the radio are old people. But that's another story.
If you broaden the view, and broaden the definition of talk radio, some of the most popular talk show hosts who reach younger audiences on FM are actually music DJs on rock stations. Listen to WMMS in Cleveland. This is a heritage rock station that has reinvented itself as a talk station that occasionally plays music. Maybe 5 songs an hour in morning drive. You'll hear the same thing on KISW in Seattle. These are stations that identify as music stations, but are actually talk stations. And they get huge ratings with people under 50. Isn't that who talk stations SHOULD be targeting?
I agree with your comment about 50-year-old bumper music. If a talk station is playing old music, it will reinforce it's programming to old listeners. Especially if the old music is pop music. All you have to do is see the demos on stations that play that music regularly. It's all over 65. Talk radio is forcing itself into obsolescence by how it's being programmed. Music is just part of that.