That's why so many people hate the ending. Because there are too many reasons to. Everyone must found some.

It's really that bad.

Because it failed on so many different aspects.

When some say it's OK to have plot holes, they forgot about the lack of closure.

When some say it's OK to be ambiguous, they forgot about Bioware's false advertisment.

When some say it's common for game developers to trash talk, they forgot about all player choices became pointless.

When some say the ending can't be so long to reflect all your decisions, they forgot about Shepard's broken character in the last conversation scene.

When some say it's in fact natural for Shepard to act like that, they forgot about how illogical the Reaper's truth is.

When some say it's just beyond your comprehension, they forgot the sudden change of the game's main theme in the last 10 minutes.

When some say that's a good dramatic twist, they forgot about the unoriginality due to the similarities with Deus Ex Human Revolution ending.

And when some say those anti-ending guys just want happy endings, they are simply wrong.