May I come up to the artistic defense of my beloved Led Zep?
The fact that Zep stole blues riffs without proper credit is well-established and proof galore. But I never saw them as the second coming of The Beatles.
Zep's importance as an influence is not in their songwritng, it's in their sound and the folk- and world music influences they added to American blues. They took those American old bluesers' songs and turned them into a new art form with their esoteric, yet larger than life presentation of them. The sound they forged was lightyears away from the originals, much farther away from the originals than say Bluesbreakers, Yardbirds, Cream, Fleetwood Mac, Ten Years After, Canned Heat, Savoy Brown, Foghat etc. Zep were hugely influenced by the blues, but not overawed by it. The bluesiest non-blues band on earth. They took the blues somewhere else, sonically and culturally. For that they deserve credit and it is their lasting legacy.
The sour note is that - probably at the instigation of their prince of darkness svengali Peter Grant -they attempted to withhold deserved royalties from people who had a fraction of the wealth (and fortune in life) of these four young white multi-millionaires. That was a real cheap shot.
But they didn't just steal from black guys.