Well, this is one topic I have thought a lot about, and since you asked…
Back story, I first listened to the Grateful Dead when I was 12, 1974, friend of mine introduced me along with other aspects associated with the band…and, no, my name refers to the fact I’m a chemist, not my former activities…honestly…
1976, I’m 14, my 16 year old brother convinces our parents that it would be fine for us to attend a Grateful Dead concert, we still laugh and marvel to this day how they thought that would be just a peachy idea, you boys run along and have a gosh-darn, wholesome wonderful time…
So, we’ll not recount my memories between 1976 and 1995…fast forward to 1998 when The Other Ones (the main members being Weir, Lesh and Hart, Bruce Hornsby as well as he was in the last iteration of the GD), they had two guitarists that were OK, but it was too soon, too raw, I remember just being disillusioned…
When ‘The Dead’ toured, including Kreutzmann, the version I saw several times featured Jimmy Herring (now a member of String Cheese) and Warren Haynes, and suddenly, OK, it’s not Jerry, but holy shit, it’s damn good, I have to say those shows really embodied or at least, celebrated a Grateful Dead concert experience…
When Phil Lesh launched the various “Phil and Friends” tours, he absolutely recreated the feel of a GD concert, bringing multiple musicians, featured artists, and playing the entire catalog of the GD, bringing back oldies and goodies…one of my favorite shows was when I took my then-16 year old son to see P&F at Bethel Woods where the Trey Anastasio Band was one of the opening acts…Trey played the second set and it was unbelievable…the second set was the show they played at Woodstock (Bethel Woods is built on the Woodstock site, not directly, it overlooks the bowl), the encore was the last three songs the GD played at Soldier Field, Jerry’s last show…
Since then, I’ve seen Further multiple times, saw one of the Fare Thee Well shows, and Dead & Company twice featuring John Mayer…which brings us back to the OP’s question…
The guy can play, no doubt. To me, the only one that could possible capture and really give a glimpse into a GD show is Trey Anastasio, he gets it, Trey is not Jerry and he never tried to be, but he can capture a moment with the Dead…the first time I saw Dead & Company with Mayer, my thoughts were, he’s got all the chops, he’s got all the moves, but…the second time, I looked around at the crowd, I saw all the old hippies, and all of the young’ens screaming and dancing like it was 5/8/77, and it just totally turned me off…I don’t know how to explain it, but I felt like I just paid $120 to watch a really good Dead cover band with some former members…Hart and Kreutzmann still have it, Bobby’s fading and God bless Phil, given all his ailments, is still giving it his best, but…
The very first Grateful Dead show I saw…the lights went down…the crowd went wild…the band wandered on to the stage and noodled on their instruments…and I had one thought…and it was the same thought I had over 120+ shows over 19 years, that when the lights went down, when the crowd went wild, there was no where else in the world I would rather be than right there, right then…
Does Mayer capture that? No. Is he good - yes, the man can play. Will I ever see them again, no, I am done…