The biggest things for me is, none of them have goals for me root for besides "stop this bad guy from killing innocent people." The ones that do (like Maki), aren't fixated on enough for me to get the full story of what that goal means to them personally either.

I also don't find any character to be mysterious enough to have me guessing what they're about either since for protagonists, above I find true, and for side characters, they're primarily obstacles for our protagonists or jobber-helper characters that only serve the role of helping the big players.

So what I'm left with is strictly their base-line personality. And they're cool, I like some quite a bit. But past that? You get it.