@Zero Yeah, in the context of reviews it does seem that being "more of the same" impacted some of the review scores. This is something typical for Nintendo games, and maybe happens to other games too.
And like
@Cubed777 said, I think some reviewers also found it more difficult than Returns. I actually felt it was a little easier, though that could just be because of the abilities of the two new Kongs, and also because I was used to the formula.
Plus, I think some reviews were also trying to justify it as a reason to buy a Wii U and didn't quite live up to that, whereas Returns didn't have the burden of selling Wii systems.