"With the possible exception of the UFO of the late 70s."You may have mentioned them before, but I can't place them.
What made them different, or palatable, even good?
UFO were serious rockers. ....especially when lead guitarist Michael Schenker was with the band. Very good musicians, very good songs. .....AND one of the few bands that could pull off the "power ballad" (although they didn't play too many of them).
Their 1979 release Strangers in the Night is one of the top 10 live albums in the genre's history, imo.