I don't think he's a great technician on the bass. He doesn't either and was quoted in the early days as, "Just following Ringo's bass drum", but as a musician he played exactly what was required. Which is never a bad thing.
Then, when the Beatles went into creative overdrive his bass lines kept pace. He changed the way bass players thought about bass lines and empowered all of us to use our elbows and move right up to the front of the song.
I think you can talk about McCartney the bass player in the same breath as James Jamerson. They were both imaginative, creative and important to the instrument and they released bass players from the 2/4 "hell" that had been their lot up to that point. They opened that door and made everything we know today, possible.