Yes and no, yes its reuse of old jokes is making them less funny and to seem stupid. I also find some of the jokes to be just in poor taste. The domestic abuse episode where Quagmire takes care of his sisters husband once and for all was really kinda harsh. I watch the show for comedy, I know it's an important issue to educate people on, but they either mocked the women or victimized her. In the end he killed the husband and that was that. That doesn't really solve anything and seemed more like a try at shocking people to drum up more publicity. I'd rather not see that episode again to be honest.
I will say I will say that some of their other episode I find really funny despite the seemingly racist jokes. I'm Jewish, I still laugh at Mort, because some of it is true and if you can't laugh at yourself, why are you watching?