I feel that way about Geddy Lee's voice, but their music is so good that I still listen to them. As far as Zeppelin and melody, harmony, and structure, it is there in spades, but it's the guitars and keys of Page and Jones. Most of the songs after the first couple of albums were deeply orchestrated, but used layers of different sounding guitars and keys instead of a traditional orchestra. A listen to Archilles' Last Stand with a good set of headphones will explain what I mean. Each time you listen to a later Zeppelin song, it seems like you can pick out a different guitar part hidden in the mix behind the main guitars and Hammond or Mellotron.
And I agree, Floyd was awesome. I can listen to Gilmour solo all day. Every time I channel surf and find him on Palladia, I stop and listen to his live music. They gave Clapton the title of "Slowhand", but Gilmour is the one that deserves it.