Fictional rock and roll bands are always rubbish, imo. They're usually thinly-veiled analogues of real ones but the music is never as good; and can't really ever be, not having had the time to permeate into the culture. And whilst we accept the likes of Jagger, Bowie and Dylan as fixtures of life, if you'd only ever seen them guesting in COLUMBO for an episode, they'd just look like the phoniest tossers ever.
The other big problem is that rock stars just are tossers, by and large. They only seem to make sense on stage. Off-stage, they're preening, pampered egotists. It's pretty hard to feel any sympathy for them.
I'm hoping, of course, that Scorsese and Winter are aware of such pitfalls. It'll be interesting to see how they get round them, if they do.
I don't think this is going to be about personalities, but rather the industry itself and how it developed into what it became ...and ultimately it's demise.