The guitar is a funny instrument to learn. It translates so well to graphs and video that a novice guitarist can get to the point of sounding pretty good relatively quickly. I don't just mean learning chords and being able to play for a sing along at a campfire, but playing single note riffs and things that sound virtuosic. If you want to know how to play the impressive lick in a particular song with a little finger tapping thrown in, there's someone on You Tube who will show you how to do it. Then it is just a matter of watching where your fingers ago and learning by imitation and repetition. It still requires patience and dedication, so I'm not deriding that process at all, but at the end I find the student has mastered a lick but is too often no further ahead when it comes to knowing what notes they are playing when they play that lick.
I have students who if I ask them to show me their best playing can sound really impressive, and if I only heard them on one or two songs I might call them really good players. And their musicality (tone and rhythm) is often good. But the problem I observe over and over is what I call a peaks and valleys phenomenon, where they can do something really flashy that demands some technique and technical, but they get stumped if I say "try playing that C# an octave higher, I think it'll sound better." At that point, I watch them slowly work their way from the lowest string upwards, trying to figure out where that high C# is. What to most trained musicians would be a split second process takes a good 15-30 seconds of deliberation and figuring out.
While instruments such as violin or clarinet demand a slower development of technique that progresses alongside reading skills and theory, the "learn by video" part of guitar playing is a great tool but also a handicap. Learning licks by video usually outpaces any knowledge of how chords are built, notation reading, theory, and even a basic knowledge of the fretboard beyond seeing it as a graph where fingers go. Someone can play really flashy stuff (their "peak") but then have gaping holes in their knowledge of how to make up a solo or even play common chords like a Dmin7 (their "valley"). Not so long ago even self-taught guitarists had to learn stuff slowly by ear from recordings, as there were no videos, and in so doing they learned to hear the connections between different chords or "licks" that might go with them in a solo, even if they didn't learn theory or notation. Paul McCartney doesn't know how to read music, but he certainly knows how to turn an A triad into an A minor triad. But now young musicians see where to put their fingers to do complex things, but often don't hear how things fit together to do basic things.
I find my teaching is often about trying to help students see the gaps in their knowledge and even out the peak and valley graph that would describe where they are at as guitarists. I'm spending a lot of time trying to find ways for my students to know where to put their fingers when I say "play a G anywhere but on the two lowest strings." Mostly I continue to figure out the best way to deepen my students knowledge of their instrument so they can understand music better. I've put a few things that I think would help with fretboard knowledge here but I'm realizing I probably need to do more video tutorials. And I find myself asking my teaching friends: What is the one thing you wish your students could do better and what do you do to help them with that?"