I used to play solely by position. I started box scales on the low e string in the key of the song and would work my way up.
Then I learned blues scales (playing only by position still)
Then I learned penatonics and began to see how relative minors were related.
Then I learned modes and what they looked like and tended to prefer certain modes to others, e.g. mixilodian and dorian. Interesting thing happened on the way to modal learning, all of a sudden I needed to learn intervals. Why? Because you can't play a dorian mode unless you know the interval away from the root. You can't play the mixilodian unless you know the 5th of the root.
So now I'm into intervals which speak to me by saying okay we have a I VI IV V (1 6 4 5) in the key of C. I know that the six is minor so I'll look for the dorian or the mixilodian in the key of C. The results would be to play the major on the I, the dorian (as I prefer it), the 4 and 5 can take the mixilodian or the majority of the dorian and then make sure to hit the root a bunch of times in the process.
I've been studying jazz which introduces the study of sevenths, releatives and substitutional techniques. So all of a sudden, lets say I choose to play a major pentatonic, I can add the b5 and b7 and come up with a hybrid jazz/blues sound which when used as passing notes allows me to smoke up the fretboard. All of a sudden things are opening up for possibilities and I haven't even scratched the surface.
That's a long way from just playing the box scale starting on the root.
