Hi,
At least as far as "Let It Be", I think that George was getting tired of the over production thing in their music and it shows in the album ... it's more than ... let's play ... and I think that the concentration and rehearsing to get it done, took its toll, and the film showed it ... but it also showed in the end, what very good musicians can do!
The sad thing, from my point of view, is that both George and John took on this "street" recording, kind of thing to their next couple of albums and I never thought they were that good, and in George's case, it was about the music ... either it shines or it doesn't, and that's that!
I don't think it did as much, and really ... all it said, was what we already knew ... it was hard for a "studio" band to do well on the street, or the stage, in those days ... and I'm not sure that George, or John, wanted to deal with the studio a whole lot for a while.
But for all this and that ... the mixing in there is strictly about rock'n'roll and the peripherals get wasted ... just like in Portland ... you'll be damned if any band's keyboards or woodwinds will ever be heard on the stage! You can only hear, drums, bass guitar and maybe some vocals! Guess what those recordings had? Has anything changed since then? ... NOPE!