I don't understand the idea that it's too early to judge. Maybe it would be too early to judge if these guys were new to film-making, but they're not. They have a well practiced track record of utterly awful movies behind them. This includes Bay, Liebesman and Platinum Dunes as a company.
These guys have been working over a decade and have no understanding of what makes a good, structured movie. It isn't "too early" to know that at all. It doesn't matter if the turtles are aliens or not, or mutants or not, or teenagers or not. Hell they could stick to every single detail of the origins and events of the original comic run if they like, it still won't work because they are utterly awful film-makers. To have any sort of anticipation of this movie must mean you spent the last decade or so sticking your fingers in your ears and singing "la la la I'm not watching" every-time you've come across anything this company as put out. Which in all honesty, when I look at the state of Transformers, Halloween, Texas Chainsaw Massacre, Friday 13th, Nightmare on Elm Street, etc....I sometimes wish I had done, it might have saved me the dull plodding headaches I get now every-time they buy a property I once enjoyed.