@mrcompletely I agree with you on this, but for me it is more than just Garcia. The Grateful Dead functioned as a democracy. There was a push and pull that anyone on stage could step up and take part in, whether that was a musical dialog or bringing material into the band, etc.
I have certainly heard bits of that in postGD configs, but it always feels like there is a controlled space for it to happen. It is more about nostalgia than it is exploring new territory.