They pay the performers if the performers own the material being played. If the performers don't happen to own it then they are out of luck. In the latter case the performer was presumably paid what he demanded or was offered. If he was never paid anything at all then he may have a case that something is owed. It all comes down to the deal the performer makes. If he gets played for a sucker once than he has paid the dues most have to pay to get a start. If he lets himself in for a screwing after that then he isn't looking after himself
The artist who isn’t seeing anything from the publishing side of his songs may not be seeing anything from the album sales either. But this isn’t the fault of radio.