The problem visually for me is that they went with Paul Dini's art style, if not him exactly. (I think that was the guy, I could totally be wrong.) Paul Dini is the same guy who did Batman Beyond and Batman TAS (the later seasons, like 4+ I think), and also the Superman Cartoon.
His art style worked for those, I think, because....at heart they're comic book characters and visually they were still instantly recognizable as Batman and Superman. You're very used to seeing comic book characters in different art styles and even kiddified, in a manner of speaking.
Transformers....Really they've only done them one way: big, blocky, and mechanical looking. Lots of squares and tubes, I suppose. Beast Wars was different with the CGI and beast concept, but past season 1 you can really see them go back to that "mechanical" style of Transformers.
Beast Machines was a sort of a different matter, but it kept the same principle. The bad guy's all had that mechanical look, while the heroes were organic. Hard edges and squares versus smooth lines and curves, I guess.
The problem with this particular art style is not just the fact the bots and cons look.....kiddified, is the best way to put it I guess, but it just seems to lack the "mechanical" nature I'm used to. That and the proportions on some of these guys is just crazy weird. I know, talking about proportions when referring to Transformers is awfully subjective, but this new show just takes it to a new level, especially with the kiddified art style.