Doesn't seem like the were "ruined" or a "joke" last night. This is why Andy Goodwin's content free rant on Slate.com was annoying. It was clear they were going to play Stairway to Heaven and it was clear that it wasn't going to be the focus of the concert either, but instead the question of whether the band could put the energy and polish after two abortive attempts on stage, into a full set.
It seems from the people who cared about it that that happened.
What ruined Zepplin was the massive amounts of drugs and alcohol tha their drummer consumed leading to his death. Not a song, over indulgence. And as far as I can tell, over indulgence was part of their brand from the beginning. But then Andrew Goodwin wasn't about to let facts and basic methods of scholarship stand in the way of his self-promoting egotism.