The problem is that Capcom didn't put any effort into actually celebrating their 2 biggest franchises. Instead they found a fan project that did just that, and put their name on it, disguising it as a "free present for the fans", when their only involvement being slapping their logo on it. But it's not just this that people are bitching about it, of course, it's a culmination of horrible decisions by Capcom in the last 3-4 years (especially in regards to MegaMan), and for some people this is the straw that broke the camel's back (I think the camel's back broke LONG before this though).
That said, I did play through it yesterday and it's pretty fun. The level design isn't at the caliber of the NES games and the game is pretty easy, but the concept and execution is solid. I like the idea of adding ultra attacks to the boss fights and most of them are actually fun to fight (except Ryu who is way too easy).