sigh. I'll only ask you this. What would you think of it if they made a Who framed Rogger Rabbit completely in cgi?
Haha... you have unfortunately stumbled across a big Richard Williams fan.

t: I loved Who Framed Roger Rabbit, which also had a paper-thin plot like TMNT, but still holds up to this day for its visuals and the world which it created.
But the point you bring up doesn't apply to TMNT. They went with CG with this new movie because 1.
No one was willing to produce another live-action TMNT; 2. CG in a way suits the genre of TMNT very well. You can make characters do things in CG that simply can't be done with actors in heavy rubber suits, as well as get a much wider range of emotions. I loved the overall look achieved in the movie -- it's like a hybrid between realism and an actual comic book. I think it only looks plastic on pirated versions. In the theater... the experience is so different even from the HQ clips online. And yes, I'm taking into account the entire world of TMNT -- not only the live-action movies, but also the original comics (as did the director).
Now there is a fundamental reason why another Roger Rabbit feature should
never be attempted in CGI: Roger Rabbit is a 2D,
hand-drawn "toon" in his universe, which is clearly established in the first film. You can't have the whole movie CG because then it actually goes against the practically designated rules established in the first movie: there are real people, and there are animated people. If everyone and everything becomes CG, then everything this animated, but now there are neither real people nor traditional toons; everything becomes a late-20th, early 21st century mix of real people and hand-drawn toons. (Maybe a result of intermarriage, but I digress.)
But with TMNT, CG as a MEDIUM does not go against "canon," rather it supports it. What matters is that you create a world that bridges the real one to
the urban mythology of the TMNT. I really think they succeeded in that. I hope that, if there is a bigger budget for the next film, they will expand on what has they began with TMNT 2007.
Now was this a GREAT film, technically? No, no, and a big NO. There were tons of things that were done wrong as people have pointed out a million times, but that doesn't mean TMNT can't be enjoyed or commended for the things it got right: the details. Rarely do movies manage to hold together because of details, but this one does, and that's why a lot of people are surprised at how much they enjoy it.
Not to say that details aren't enough for most people. (Most people agree that in terms of quality, the new movie is only B or C-level). As far as liking the film, I think it depends on what you value more: the characters, the plot, the humor, the action, the bad guys, the
medium (which in your opinion, is extremely important), or a complete replication of your childhood experience.
And by the way -- if you think the consensus at the Hype is overrating the movie, take a look at the traffic in this section. There isn't much, meaning that not enough people have seen the movie, or that not enough people care one way or the other to voice their opinion.