Moving outside of guitar-based music, there are virtuoso pianists who can play Bach's Goldberg Variations or The Well-Tempered Clavier from memory, evoking joy and awe in the listener. But then there was Bach, the genius who wrote--and could play--the pieces in the first place.I've noticed over the years that many threads about well-known guitarists, such as Hendrix and Clapton, contain remarks along the line that any intermediate guitarist could play their guitar parts, as though that puts the guitarists on equal footing with the original. It seems to me that view doesn't take into account several factors.
1. Guitarists like Chuck Berry, Eric Clapton, Jimi Hendrix, and Eddie Van Halen developed very unique musical voices that were innovative, highly recognizable, and hugely influential. So, even if you could copy their work verbatim, much of their importance was in the development of their unique musical voice.
2. In the cases of Hendrix and Clapton, much of their work is off-the-cuff improvisational musical statements. For someone like Hendrix, that includes much of his rhythm playing as well. So, learning something note for note is quite different than being able to create something on-the-spot at gig tempo, that is unique and musical night after night.
3. Also, not being able to copy something by another guitarist doesn't mean you are destined to mediocrity. There are some amazing guitarists that arrived at a unique and influential musical voice, in great part, because they were not able to copy others exactly. B.B. King comes to mind.
A final thought. If you could paint a copy of a famous painting, it might indicate an advanced skill level, but it would not, in any way, indicate that you were on the same level as the original artist. Reciting a famous poem is not the same as writing the poem.
Back to guitar-based rock-related music, I'm astonished by some players' ability to play note-for-note renditions of guitar gods' songs, but I'm always going to be more impressed by the people who wrote the songs in the first place. As you noted, often those musicians were doing something groundbreaking at the time. On top of that, I've always been wired to care more about the song itself than someone's technical proficiency. For instance, when I see somebody absolutely shredding on Instagram, I think, "Damn! That's impressive!" and then more often than not forget just about every note I heard within five minutes.