One thing that we miss is that Jerry's solos really, really cut through. I've read in several different accounts that Jerry liked to keep his on-stage amp volume up really high. I think he personally controlled the way his solos crescendoed with his own personal volume, and when he played really loud, everyone else turned up and the drummers hit harder and the place exploded.
They didn't have amps on stage in the later 1990s (none). I think what you are referring to is how Jerry's guitar was electronically modified- that the guitar electronics went pickups>dials and switches > went out to the effects loop(s) and pedals, etc. > CAME BACK into his guitar again and from there he could adjust the total tone. Something about this allowed him to have better tone even when he was turning down the volume nob, which he saw as a problem.
But here's the thing: John's guitar does it too. So do a lot of deadophile guitarists.... I would, if only I had things like a big amp and more than 2 effects (I'm too cheap to buy effects). And he had a master volume pedal so he could control the sound without using his hands. I think it would be argued his style of playing, masterful playing really, cut through everyone else because of his technique. It was not the loudness per se...
So I think the argument here is that the band is not creating the crescendos. I don't know how I stand on the argument, but I'd have to listen to a show. I think I've been overall very impressed with them (crescendo is a very important aspect of Grateful Dead music, IMO).
On another note- I just saw DSO play in Los Angeles and they blew me away- crescendos aplenty!!!!