I definitely get what you're saying. There are some points here and there where it feels like there's a galaxy threatening war going on, but they are few and far between. On the other hand, I don't think it could have been any other way. It's a linear shooter, just like ME2, with no space exploration to speak of. I mean, it would be pretty impressive if they actually did manage to make it feel like there's a huge war going on, don't you think?
I'll decide how I truly feel about it after I finish it, but so far I must say I'm not disappointed at all. It's exactly what I was expecting it to be. Not what I wanted it to be, but everything I expected it to be. Most of my disappointment came after I played ME2.