its not something I've personally experienced (my last paid work in broadcasting was 20 years ago in the tech/engineering side, my current day job is in IT/telecoms for healthcare), but it is a known problem here in England especially for younger people (<50 years old), female broadcasters, those of minority groups etc, especially on commercial media and has been for a good few decades. on the rare occasions I listen to UK mainstream radio it is mostly the same presenters from 20 years ago and the companies simply aren't hiring (or if they do the pay is less than working in an office or callcentre)
One problem is that a lot of commercial stations consider the ads to be the most important content and don't even care about anything else!
This is precisely why many people no longer listen to "normal" terrestrial radio and prefer podcasts or online content or even pirate broadcasting (its still a whole subculture in the Netherlands and many of those involved are often our parents age group
)