Wait, so are you saying anime's lost its testosterone? Because that kinda stuff is still very popular. Kill la Kill, SAO, Dragon Ball BoG, Jojo- it all still exists. In fact, all things considered, that does put things in perspective, why AoT is so popular.
I do see this growing trend of mostly one-dimensional protagonists getting a lot of love because that look cool or have moments of budget, and I think Eren fits the bill to some extent. He's not really that interesting but, at the same time, he has The One syndrome and can turn giant which, to the masses, makes him an awesome character (another anime I listed takes this in spades). But for me, even when I see moments of badassery, when they involve a character I don't like I just can't get into the fights themselves. I can acknowledge that they are well done scenes (or...well, I'll see them more for what they are), but because I'm not really hoping the protagonist will come out on top (or the "good guy", I should say), I'm not nearly invested in what's going on. But it does well for the show's popularity, and if that's what you enjoy about it, more power to you.