First, great players make mistakes and often. It's just that you or I might not hear them unless they're really egregious. Part of being a pro is just moving on from a mistake.

Yet, how does a player get that 'super power', and they do make them. Having had enough contact with known and 'that level' guitar players the answer is this; practice. Ok, not a wow answer but the actual answer is, they practiced endlessly.

I'll share a story that isn't from someone I know but a (great) guitar playing friend who was friends with Zakk Wylde. What he told me was that Zakk, when he was coming up, practiced up to 12 hours a day. He was that dedicated. Whether or not it was actually 12 hours on any given day, he just practiced and practiced.

Same with a guy I had the chance to meet and attend a workshop with, Laurence Juber (McCartney's Wings and much more). I've seen him several times too but, throughout a couple of hours of this workshop (of about 8 other people), he talked about discipline. He's been playing for decades and still spends much time practicing.

So, is it a barrier to break through? More or less, yes. Even for me when I started playing in the 80's. By my 5th year, I was decent. But then I just wanted to get more command of the instrument. It was the 80's, so I wanted to shred. So, I would just drill on something until I got it down. I would also do hand stregthening stuff too that was't playing but just drills on the fretboard. My playing jumped leaps and bounds in that little window.

Someone I know posted a video of his band playing their first gig. I get the impression they practiced a bit but not a lot. I watched the guitar player (cuz that's what we do) and though he did a solid job, the guitar was playing him. At any given time his playing could have gone off the rails if he did not laser focus on what he was playing. The stuff wasn't super-complex, in a punkish sorta way. But he was on the razors edge. He practiced enough to be able to play but not enough to be that next level.

When I jumped leeps, I was practicing hours a day. Hours and it was physically obvious.

To me, there is no substitute for hands on the instrument...Today, I don't have time to practice like that so my playing is not exactly otherworldly (and can be a wee sloppy at times) but even now I can still have a command of the instrument simply because I went through the excersize of overcoming a physical limit years ago.