Spend some time listening to drums on some of the best Beatles songs: Ticket to Ride,
Come Together,
Rain,
and many others!
Singing? Not so much, IMHO.
I think they used his voice on the right songs.
Octopus’s Garden, wouldn’t have worked with Paul, John or George singing it.
True. With Paul’s melodic bass playing, it’s hard to drum without stepping all over the bass lines.
Also if you hear George’s version of “It Don’t Come Easy”, you can hear why he ended up lending it to Ringo.