The production on most of their stuff was not great to my ears.
Do you mean production in terms of fidelity, or production in terms of the range of sounds used, the tones of each instrument and how they were captured?
I think especially the earlier material sounds as though it was recorded with fairly primitive gear gear - magnetic tape, consoles etc hadn’t really advanced to anywhere close to where they’d be even by 1970. An even bigger factor is how people listened to music back then. I think Abbey Road holds up pretty damn well to modern standards, largely in part to the EMI TG12345 desk getting used, stereo being slightly more established, having more time in the studio etc. I think recreating this sound now would be a very tall order - the mics alone are among the most high end and revered you can find, the outboard is similarly regarded as the pinnacle of what is available. It’s also a world leading studio, the top engineers, George Martin etc.
In terms of production in a more arrangement sense, I think it’s pretty amazing what they achieved. There was a constant pursuit of new sounds, and combining things in ways that hadn’t been done before. So many different instruments, both old and new (at the time) were combined in creative and musical ways.
Regarding Ringo’s drumming…. I think his genius stems from the creativity of his parts - there are so many songs that have very unique drum beats that would ONLY fit with that particular song and don’t really confirm to typical patterns. Come Together is an obvious example, but there are so many that are like that (In My Life, Here Comes the Sun, Tomorrow Never Knows).
The other aspect to his drumming, is he has a VERY distinctive and unmistakeable sound that manages to ooze personality and yet never impedes on the song or gets in the way. Absolutely no one is able to imitate his exact groove, it pushes and pulls in a very unique way that only he can pull off.