He was satirizing a certain kind of clueless upper middle class suburban worker type, in those Vacation films at least. Maybe there, his slipping into becoming caustic and slightly unhinged was a funny contrast to the character.
And maybe also he was able to keep a distance from the character and not get his ego entangled. “I’m playing a clueless dummy. Of course I’m never like that.”
He can be funny too. He was funny in 3 Amigos, and in Community. He just seems to have always had his negative personality traits tanking the likelihood of him working with the same people again. With him then not working on those traits, just blaming everyone else instead.
He could still be working with Dan Harmon, or Steve Martin and Martin Short, or any of the people in Hot Tub Time Machine which was stupid fun. But, in the parlance of our times, he played himself. I hold out hope, as I do for all people, he can still learn.
