So was that a first for the Mirage Turtles in animation?
In such a literal form, yes. But the '03 series was fairly faithful to the comics' continuity and concepts and adapted a number of the comics' storylines pretty closely. At least until the last couple of seasons that took it in a sillier, younger-skewing direction.
Some say it was trying to put down the 80's Turtles, I don't know if I agree with that but I think they came off well regardless.
It was definitely meant as an affectionate ribbing, not a meanspirited putdown. It was definitely caricatured, but not out of malice.
Maybe it was just nostalgia but I loved their good-natured goofiness and thought they had a lot more personality than the new ones.
I didn't think their personalities were all that well-represented, really. They all seemed pretty uniformly portrayed as childish cutups, laughing their shells off at anything remotely amusing, and that doesn't seem accurate to me. Leonardo was fairly serious, at least in the early seasons, and Donatello was more the quiet, inventive type. Really, the only character whose personality was profoundly different in the '80s cartoon from other adaptations was Raphael, whose tough-guy personality was replaced with a sarcastic wise-guy persona.