The show was funny because Larry David is a cantankerous curmudgeon who's afflictions just happen to be a hilarious source of comedy material for him to write with. Also, the strength of Seinfeld's costars let them carry the shows comedic acting and timing.

The show is funny in spite of Seinfeld, not because of him. The fact that he insisted on doing those god-awful stand-up bits on every episode is all the proof you'll ever need about that.