Agree.
I can think of no more polar opposites that Marx and Leno.
You Bet Your Life was designed around Groucho, who was quick witted, and a master of impromptu banter with the "contestants". He was a master of the double entendre and the quick joke.
Leno, IMHO, is a slow witted guy. My impression from his Tonight Show time was that he really did not get many of the jokes he read from the cue cards. Especially in current event and politics, which I think he has little interest or knowledge of. In his interviews he seemed to have a few talking points written for him by the staff, many of which he seem to really grasp.
Even in his car show, which is about a subject (the subject ?) upon which he has knowledge and interest, it seems robotic and bland.