Parts of Unity are incredibly frustrating. Serialization is poorly documented and is inconsistently implemented, the GUI sucks, and the editor can get out of hand quickly with large projects.
However, It is rather strange that your game dev teacher is talking about unity from the perspective of a player when your teacher is a developer yes?
Also, before GDC with UE4 and CryEngine, consider what options you had before unity? They were far and few between, and Unity sure beats writing your OWN engine.
Now of course this could limit you if your game doesn't fit well with what Unity provides. There is a statement that is made often on these forums "Make games, not engines". products like unity exist so that small teams or possibly 1 person that works their ass off can actually make a decent 3d game.