People ragged on it because on the original release it was mandatory to grind it for dozens upon dozens of hours to get the best ending in the single player. Unless you had a near perfect save file, which had so many esoteric decisions required that nearly nobody did without a guide compiled after seeing the payoffs in ME3, you were forcing people who were fans of a single player trilogy to now play a multiplayer game just for worthless "points."

People already hated the points system for a long list of reasons, but locking them out of an ending unless they grinded more in a multiplayer they didn't want made it even worse.