These seem like fairly unrelated issues, and I have no insider knowledge. I happened to like ME2, although it seemed like all wind up and no pitch, and the boss was obviously ridiculous. My only guess is that they figured they couldn't really rehash ME1's structure without it going downhill, so they tried a different angle. Incidentally, I think ME2 also drew upon a variety of space opera tropes that hadn't really been captured in ME1, so I think they did a pretty good in that respect, too. That said, I didn't like ME2 enough to play ME3.