Phil came from a 20th century jazz and classical background. If you put his playing in the context of a jazz group like Bill Evans with Scott LaFaro or the role of a cello player in a string quartet, it makes a lot more sense. The Grateful Dead were more interested in following their whims of the moment in reinventing music and in some cases it meant a lot of effort in reinventing the wheel and in others it meant taking traditional forms (like a contrapuntal bass line) and recasting it in a rock context. The journey meant more than the end product, so objective analysis in the context of pop music from 40 years later is somewhat futile if not meaningless. any expectations were confounded at the time, so to expect a conventional bass line out of Phil would be an exercise in frustration. We have plenty of kick ass conventional players, why not enjoy him for what he is? He's like the rest of every aspect of that band; charming, yet temperamental.
I, like others in the thread, lost a lot of interest after Keith left. I had some fun listening to Brent, but his approach was too heavy handed and knee-jerk rock and roll for me. Their playing lost a lot of possibilities after he joined, although it probably wasn't all due to him. Saw my first show in June '76, so I missed the Wall, but that show did have an equally interesting rig that was essentially a huge Sansui powered home hifi. Sounded amazing with one rig for instruments and one for vocals. I guess inter modulation distortion was a much bigger problem back then (which is why the wall had separates PAs for each instrument).
I inherited a monster Bag End 2x12 cab that looks very much like a Wall cabinet. Same woods and aluminum clamps. Doesn't sound that great and too heavy to move, so it sits in my basement.