Ah, DA2. I never get tired of pointing out your flaws.
The reused environments were plain inexcusable and should have knocked a full star or point off of any review, anywhere. When a dev with plenty of money and support makes a conscious decision to cut an exceedingly obvious corner, it is every responsible critics' duty to call that shit out. This, incidentally, is why the Escapist reviewer rightfully catches so much flak about his bullshit perfect mark. When the devs do something very objectively wrong, you don't get to bypass it on account of personal preference - at least not if you want anyone to bother reading your reviews anymore. The reused environments were especially egregious given the game's attempt to reconcile them with an admittedly smaller scope.
Rock, Paper, Shotgun did a fantastic job pointing out the many narrative faults of DA2, including the "in media res" intro failure (this is supposed to be exciting, but it's just obnoxious), the ineffective deaths of relatively unknown characters for "dramatic weight" (I guess I was supposed to care about that person, but I'm still not 100% sure who the fuck he/she was), the intense sense of detachment resulting from multiple time leaps (how did I end up being this/here, and why didn't I get to enjoy that development in person?), and the overriding suspicion that none of your decisions actually impact the final outcome (they don't).
You can find plenty of write-ups on the flaws of the revamped combat system, but chief among them are: the limitations in party setup (only one real healer and only one real tank); the spawning or waves of enemies (aesthetically idiotic because they involve roof ninjas, mechanically idiotic because they turn the game from one of measured tactical deployment to "spam my cool downs right away so they're ready for the next wave of roof ninjas"); the animefication of combat (my dark and gritty fantasy game turned into a bunch of spiky haired super saiyans flying all over the battlefield with 10-ft swords); and, last but not least, a reduced emphasis on healing magic, crowd control, and other support functions (which would have been difficult to coordinate without the now-absent overhead view anyways, right?).
The gulf you're seeing between those who hate the game and those who like it can be drawn right between PC and console gamers. Those who played Origins on a PC had a vastly different and objectively superior experience compared to the console crowd. DA2 was a marked improvement over console Origins but a fairly massive downgrade from PC Origins. As a group that is pretty continually shafted by publishers, the PC gamers decided to make an example of DA2. They tried to sink the game with tons of negative feedback, and (judging by sales figures) it actually sorta worked. Here's hoping the next DA won't cut corners or leave a typically ignored (but obviously vocal and important) demographic out in the cold.
Edit: just an addendum: I see a lot of people saying DA2 just has way more visceral and exciting gameplay. For the record: Origins had mediocre *tactical* rpg gameplay. DA2 just switched the tactical bit to *hack-and-slash action*, but the mediocre tag is still there. There are plenty of action rpgs with loads better combat than DA2, just as there were a number of tactical rpgs that offered better gameplay than Origins. Thing is: they make plenty of action games every year. Adding one more, and a mediocre one at that, to those ranks isn't exactly what I'd qualify as an accomplishment. Robbing the world of a tactical rpg, though? In a world severely lacking for them? Yeah, that's the kind of bullshit that gets you hate.
And the hate isn't just bellyaching. Games have been transitioning to more streamlined, simplistic, and, well, auto-piloted experiences for years. This is happening because publishers think this is what people want. The only way to convince them otherwise is to raise sufficient stink and back it up with disappointing financial support. The supposedly extinct old-school demographic wised up, stopped taking its lumps, spoke out, didn't buy, and hopefully affected some change. If you think that's just bellyaching, you should probably try to separate your mouth from that corporate ass-gasket.