My two cents.
First off, I've been playing a helluva long time. I did my first paying gig in 1978, and, I'd love to be as sloppy as Page.
The guitar forums are full of a bunch of keyboard jockeys who never play actual gigs, they just sit and home and obsess over the tone of their huge pedal collection, and are infinitely critical of those who do what they cannot. Namely, get out in front of a huge crowd, playing in a band, just you on guitar mostly, nobody else to hide behind, and rip it up for three hours. The guitar forums are the true "Din of the hordes". True, there are a lot of great players, but theres a lot more overly criticial wanna-bees. I couldnt care less what most of these guys think. I just get ready for the next gig I have.
So there's that.
What happened to Page? Its obvious that at some point, maybe starting in 75, that his playing became more erratic. Im not sure why but it could be attributed to hard drugs. I did read somewhere that it was suggested that for an entire year, roughly the end of the 73 US tour, thru 1974 until they began to record again... that Page did nothing but sit around in a castle somewhere and do dope.
I have no idea if this is true, but... its not like in 75 he was a blithering idiot. Just listen to Over the Hills from Dallas in 75 or some of that stuff from Seattle. Jaw dropping good.
I think the secret to all this may be that he, and the band, were constantly working from 1968 thru that 73 tour, with very little time off. Its possible that he was playing every day, or almost every day, who knows. After the 73 tour, time away from the band began to get longer and longer and it seems that with each long break, his playing continued to spiral down a bit.
I really dont know why or what happened. All I know is, he was great, one of a kind, and it was terrific being a guitar player and trying to learn, in the 70s, when he was large and in charge and almost bigger than life.