Like anything else, some sports talk radio is and can be very good. Some break the occasional news, have solid staffs of experienced people with contacts, add the conversation in a useful way.
And many don't. Part of this revolves about corporate ownership have little interest in providing the kind of resources necessary to put on a full-bodied program. And part of it revolves around this notion of "well, we're not really journalists" as if journalism came with a professional license. These shows go to media days. They conduct interviews. They read news items. They just prefer not to be held to a useful standard, so they fall back on the "there is no standard except ratings" entertainment BS.
In my experience, many radio shows are hosted by intelligent, talented people with a comedic sensibility who are stuffed to the brim with narcissism and self-loathing, and use the show as a means of working that out. Unlike an standup audience, which can withhold approval if a comic isn't on his/her game, and talk show host can craft his/her audience with nothing but "sophisticated sycophants" and "idiot detractors." On the rare occasion that a sophisticated detractor sneaks through or a talk show host is suddenly held to a standard, boy, stand back and just wait for the wrath and bloviating to commence.
I know it's harsh and judgmental to say that the radio guy generally has to see himself and be seen as the smartest/funniest guy in the room, but when your audience is that microphone, and the creative process involves some former athlete "yes man" next to you, I can see how and why it happens. The highs and lows of those folks is startling.