From the Wall Street Journal:
After taking over “The Tonight Show” everything changed. In the words of comedy guru Patton Oswalt, it was as if a switch had been flipped. Leno stopped evolving and began devolving rapidly. Leno no longer seemed interested in the art of comedy. He pandered to the lowest common denominator with material that didn’t even attempt to hide his contempt for his audience.
To me, the quintessential Jay Leno bit is Jaywalking, a sourly misanthropic endeavor where Leno derives cheap laughs from the abject stupidity of everyday folk. Leno asks these dullards easy questions, then luxuriates in a smug sense of superiority when they come up with “comically” idiotic answers. What makes this enterprise so abhorrent, beyond the overwhelming air of snide condescension, is that these easily amused half-wits double as Leno’s core audience.
To comedy writers, Leno’s massive success represents the triumph of mediocrity. It’s the tragedy of a prodigiously talented stand-up making a conscious decision to dumb down his material to reach the widest possible audience. He won over the masses while alienating comedy geeks. He came to symbolize everything crass and mercenary about comedy. As the years went on, Leno became synonymous with Monica Lewinsky and O.J. jokes. His name became shorthand for lazy, dumb and obvious comedy. To comedy snobs, “The Tonight Show” under his nightmare realm was one long Dancing Itos sketch.