ME2's ending was just terrible. The boss fight was ridiculously cheesy.
In contrast, ME1's ending may have well been a master class in game cinematography and writing.
Much of ME2's story is terrible (some of the side character stuff is delightful, but the 'main quest' is a train wreck).
My point was that ME3 was doomed because ME2 utterly failed at bridging the gap between the strong start of an epic that was ME1 and what should have been the conclusion in ME3.
In fact 'fail' may be generous. I don't think it even 'tried'.
The entirety of Mass Effect 1 was a master class in writing, from the opening cinematic to the ending credits, that more than made up for somewhat janky (though nevertheless entertaining) gameplay.