Well, not to get into spoilers... but it's a fairly big change considering the "finality" of the original ending.
And it's not even that people wanted there to be a happy ending or whatever. There was just such a huge inconsistency/plot hole that the ending completely broke for some people (especially if you had a certain companion with you).
But yeah, certainly it didn't engender the reaction we got with ME3. But then again, it also wasn't as... problematic, to put it kindly.