The big part of the initial reactions had to do with the fact that Enemy Unknown wasn't announced at the time so people were worried series will move in a completely new direction (anybody remembers Close Combat: First to Fight?).
The other issue (post release) was how different it was from what we've seen initially - it was suppose to be set in 1950's, have first-person perspective, open-ended levels, info gathering, research and horror vibes (check this trailer and this gameplay).
By release that game turned into a third-person shooter with simpler, more linear levels, no research of alien technology and other streamlining measures. That doesn't mean the final product is bad (I enjoyed it quite a bit and the "twist" near the end was a pretty neat addition), it just didn't live up to the expectations and slowly fell into relative obscurity.
All in all I agree, play The Bureau if you want a different take on the XCOM universe. It's a decent game.