Back in the late 70s, I saw Stills about 10 times and it was the same every time, "I can barely hear him! Why does he only do those BB King riffs? Why does the rest of the band drown him out?" But, I saw him with CSNY a few times 2000-2002 and he played great!
I saw the Stones in Chile about 10 years ago. They'd play the opening riffs then go chat while the rhythm section and Mick performed. I suppose they were playing along, but you couldn't hear them. Nice gig if you can get it!
Saw CSNY also in 2000 and I was blown away. Neil Young stole the show hands down but all four of them sounded great. Sobriety appears to do wonders.
I hear what you're saying about the Stones. I love the Stones but so much of their live work just doesn't sound good --like they're simply going through the motions. There's no soul.