Didn’t make them great musicians, just a group that collected a cult following.
Other examples would be groups such as Dr. Hook & The Medicine Show, Insane Clown Possie, Phish, Primus to name a few. All had (and have) great cult like followers and yet were not great musicians.
In these two cases, re "not great musicians," you're kidding, right? Both Phish and Primus are made up of very accomplished musicians, though they tend to be very experimental.
Mark
Everyone to his own liking of course but Jerry Garcia had an evocative and complex style. Don’t go by that ‘’Casey Jones’’ crap, even Garcia wasn’t crazy about that tune. The Dead’s ‘’Dark Star’’is a psychedelic symphony. Phil Lesh the bassist, along with drummer Mickey Hart, was really the only one with any formal musical training having studied classical music at U. of Berkley. Mick Hart was a drummer in the Air Force band before joining the Dead.