Hmmmm as a former drummer back in the 1970’s Copeland was and still is one of the best drummers. Played with a Jazz feel and could rock with the best of them. Summers was also an exceptional guitar player. Not sure where you come off as saying they were mediocre.
We all have opinions. I see them as mediocre players mostly forgotten in a mediocre band with only one real talent Sting.
You apparently think they are wonderful. Great.