Iīd like to a contrarian point of view regarding Eren:
You guys are criticizing him, complaining about his lack of awareness or responsibility. About him being naive, whiny, stupid.

Let me say that I, too, want to criticize Eren, but for a whole different reason: His lack of resolve. The ONLY responsibility Eren has, is the one his dead mother. When a titan ate his mother, Eren swore to kill all titans. Thatīs his one and only reason for being where he is now, as part of the survey corps. Because of that, when Eren finally went all berserk against Annie, it was then that I nodded and said to myself "now heīs doing what he said heīd do at long last". In other words, Eren took the stance of a lonesome warrior, akin to Guts, but then became, well, really just lazy about it, made lots of friends, "enjoyed" the time and didnīt really persevere his original goal besides occasional hero speeches.
Eren lacks resolve and ruthlessness. He needs both to become stronger, and itīs probably also the very solution to gain full control over his titan body, in the way Annie had. Right now, his strenghts relies on his feelings, and thatīs no basis to make further plans for whatever. Armin would tell Eren exactly that, if heīs as smart as heīs made look like.