It's again the selective criticism nawbs on forums like to spout endlessly... first of all they do not follow the development processes of games, they know nothing of the engine powering them, what its capable of and most importantly what it isn't and thus isn't even pretending to be capable of.
So armed with a complete lack of knowledge of the game beyond the 10 minutes they skimmed over a demo with, or their time in a beta, of which they completely miss the point of being beta and treat like the final produc, they take it to the many forums of the interwebs. They will then post a half baked list of problems that may (but in most cases don't and will just be a result of their poor understanding) exist. These same people will sing the praises of other games that will almost certainly carry as many if not the same problems, but for some unexplicable reason, they ignore. There are several examples of this in this very thread, offhanded comments against the game, with no basis or reason provided.
To the OPs question about the team-play feel of it, well the teamplay is kind of woven into the gameplay via the mission system, at any one point each class will be given a mission that will earn them extra XP (to unlocked weapons / abilities throughout a particular campaign) so just by each of them carrying that out the team should be working as a tidy little unit. Varies on public of course.