The first mission is definitely boring, but once you got everyone, that's the game proper.
I'm at chapter 3, I still find aiming annoying and combat boring. Being able to upgrade only one weapon is stupid and I don't like the one I'm stuck with. Others are often useless. Robots can aim perfectly at me from a large distance, I can't (I play on hard). Teammates apparently can't refrain from stepping in front of me while I'm shooting. Corridors are boring. Level design is boring. Apparently every area ever has sand bags or little concrete walls for no reason other than allowing you to hide behind them, much like in ME2, which I find stupid. The vehicle/swimming/whatever segments are always terrible, boring and pointless.
I like the humor and the story, though. Maybe I should stop and watch videos on youtube, since I have zero fun during gameplay segments (the numerous dialogues scenes during which you can only walk at snail speed aren't helping). Bosses are also cool.
On the other hand this game taught me two things : 1) I still can be interested by cutscenes and cutscene direction in a video game, and not simply be utterly bored by them.
2)I can apparently fully agree with a metacritic score