I felt that the ending turned it's back on what made Mass Effect, Mass Effect.
It's writing, it's ability to emotionally draw a person in, it's dedication to it's own in-universe lore, and indeed that lore itself. In my opinion, the ending- minus EC- turned it's back on everything that drew fans into the series, and raised more questions than answers- and I don't mean the good kind of questions that leave you thinking, but the questions which leave you going "what the fuck, how, but that... WHAAAT." Those are rather bad questions to end a series on.
But yes. Long and short of it- regardless of opinion on how it played out, what it was, etc- is that it felt NOTHING like Mass Effect. I'm embarrassingly emotionally involved and invested in the series, and when I reached the ending "choice", I just walked up to one of them without CARING what I was choosing. I was bored. I was totally switched off.
This from someone who sat through all the monotonous boring side quests throughout the series countless times. I stopped caring. I switched off. I didn't give a crap how it ended any more.
And most of all, when it was all over, the overwhelming impression I was left with was that it felt like the ending was written by someone who knew very little about Mass Effect, who didn't care about the ending at all, and that it was stuck on there in a sort of "meh whatever I don't care just do whatever so I can do something else" mentality.
And even now- the EC makes me care more about the ending, and if it had originally been released on the disk, there wouldn't have been the fury over it. But still, even now, I hate the "choices", because they feel so "out of character" for the series, so illogical and mind-boggling, that I can't even consider doing anything but take the "Destroy" option and try to pretend that's all there was there at all.