That's a jazz thing. Jazz is a life-long endeavor. My mentor would woodshed on his Gibson L5 for hours on end. Gave lessons for five times my hourly wage and had to drive 100 miles for his lessons. He could play three note chords faster and cleaner than my teen-age cohorts could do single note leads. Bluesmen, rockers, country boys and all that have to be very good to make it big but those Jazz cats are a different breed. You have to be very good just to be anonymous.
Fair enough. But I'm not sure I completely buy into the whole jazz mystique. Some of it is very real. But a lot of it strikes me as simple posturing. Possibly my opinion is shaped by the fact I started with jazz and played that for about the first five years I was learning music, combined with how I really don't care much for how a lot of jazz sounds. Bebop and Dixieland Swing are about the only styles within the genre I could ever really appreciate if I was being honest with myself. But that's me.
In the case of the old cat, he was taking about my then half-assed knowledge of harmony and basic theory. And he was right. I didn't know what I needed to know half as well as I was kidding myself I did. And my laziness about correcting that deficiency was holding me back.
He meant well. And that's why I took everything he ever said (and he shared some other valuable advice with me) to heart.
