I abandoned using library radio. Instead, I created a smart playlist.
From the music view, click on the playlist icon and select Create Smart Playlist.
For my filter, I set “Track Last Played” in not the last 20 Days. Depending on the size of your library, you may want to increase or decrease that number.
Each time I run the playlist a get a new mix, and the songs I heard recently get shelved for 3 weeks, giving other tracks a chance.
