I honestly don't think anybody is really foaming at the mouth over the ending, it's just that we want the best possible ending to our favorite series of all time, and don't know how else to get EA to do anything about it without boycotting numerous otherwise-fantastic series'.
And the fact that we just weren't fully ready to say goodbye played a big role in it. Everything leading up to the ending was great, but just something about the final struggle gave us just enough hope for us to have a satisfying ending that when we didn't, and Shepard was suddenly yanked away from us, it felt like tearing out a part of ourselves. We'd invested so much time, effort, money, and soul into our own Shepard that for Bioware to totally glaze over the most important transitional point of the series felt like a borderline betrayal of everything we knew.
And if anything, all of this is only because the series is so compelling that you just can't help but become invested in its world and characters. No game has ever reached such a high, it's a shame that going back and playing the unforgettable and ground-breaking moments is overshadowed by such an unforgivable low.