Daniel, I'm probably not the right person to try and answer this as I'm sort of a beginner, but I think you answered your own question. I would say, yes, it's putting in the time, drills, and practicing scales slowly and precisely. I would also say that maybe playing shouldn't become so focused on learning all the time that it stops being as much fun. Get out and either play or listen to other guitar players. After you've played for a while it gets easier to pick up on what others are doing and to incorporate it into your playing.

It's frustrating and, believe me, I have the same issue as you. My stuff doesn't sound as good as Devin's, or as "pretty" even when I play it note for note with the tablature. I am getting a little better though, and that keeps me going. I'm working hard on getting my pick stroke direction right and am hoping my speed will eventually increase. In the meantime, I'll put the tabs down sometimes and just play the guitar. Out of that have come some pleasant discoveries.

A lot of the time, when I used to record myself, my playing (and singing) would sound incredibly flat. Everything was more or less accurate, but there was no emotion to it. Recently, things have started to sound more like I want them to sound in my head and I think I managed to get through that just by practicing more and practicing more intelligently. Don't get stuck on one phrase in one song for weeks — each practice session, try to work on speed/timing/accuracy with a metronome (whether that's playing scales or songs), work on memorising new songs and melodies, and play along with backing tracks. It's difficult to do everything every single time, but if you've neglected something one session, make sure to focus on it a little more in your next session. I think it's much more important to try to memorise as wide a range of songs as possible than spend a bunch of time on scales. But I might be saying that just because it's something I neglected for a large part of my guitar-playing life, since I'd just pull up a tab and play along with it.

Having said all that, one thing that might help to make your guitar playing sound pretty is making a conscious effort to phrase melodies. Try playing at different volumes — for example, try to play something really softly to make it sound calm and then maybe play the same thing more loudly to get a different emotion out of it. Music is much more about emotion and feeling than it is about speed or accuracy. Obviously, to get to the phrasing and expression part, you do have to be confident enough with a piece of music to be able to play it without conscious effort on individual notes but my advice would be to do your best to completely relax while playing in order to focus on each phrase within a melody.

Something I noticed about Devin and other clear and clean players that helped me...I notice their left wrists seem to push further under the fret board - causing a more ninety degree bend at the wrist. I tried it, because I was having some muted notes. It put my fingers more on the tips and cleaned things up a bit. It worked for me, but it takes some unlearning of years of playing with a more relaxed, straight wrist.