Guitarists of the 1960s are a dinosaur breed. They found their roots in folk, blues and jazz - the music of the past - and they added something of their own to the existing song forms, melodic and harmonic ideas of the day. What's interesting is the variety of popular music that came out of that era. Sociologists would probably mention the societal climate as a major contributor. I think the music of the era owes a lot to the artistic independence of the musicians, producers and record companies of the day. There were a lot of "beginners" in the business back then.
That beginner's mindset really helped. I'd argue that musical creativity has become increasingly stifled over the past four decades. A lot of the lost creativity in the modern era seems to come from loss of creative control, which is what happens as the business of music becomes increasingly populated by business people rather than artists and visionaries. Signed bands have always had A&R guys telling them what they "have to do" to make their next release more successful than the last. Regrettably, the A&R guys are trend followers, not trend setters. Their careers depend upon selling music, and the best they can do is to look at what sold yesterday. (Actually, what they should do is to stay out of the way.)
The music business isn't the only thing that has changed in the past forty years. Guitarists back then were - on average - not the equal of modern guitarists, when considered as technicians of the instrument. And some of them simply didn't know when not to play - some lead guitarists would solo during the entire song! That's a lost art, if you ask me. If you want to hear someone that can actually make that work, check out some of the dinosaur rockers from the late 60s and early 70s: Tony Iommi, Jorma Kaukonen, Ted Nugent, Leslie West, Jimmy Page and Richie Blackmore all spring to mind. The difference is, they played with the song, not over it. Modern guitarists would probably say that the dinousaurs had no technique. I'd argue that they could at least find a melody...