Point in case, the ones who made the choosing weren't the writers. Probably you can blame Casey Hudson on that one.
Yes, I know people have a lot of problems separating the plot from the wtf moment there, most people will tell us all about the "bad plot" of ME2, etc., but if you look closely, the plot isn't bad at all. It's a good set up for ME3, and it explores well what the reapers may want from organic lives in the galaxy. The idea of "ascension" through a very specific kind of "singularity", where mankind goes to something greater "through death" is a very compelling and rich plot idea.
Their problem was that they couldn't shock Shepard (or the players) in the larvae reaper without a very shocking visual cue. To show a complex cube without a human shape would be very cool, but it wouldn't be emotionally compelling, in the sense that we wouldn't connect with it as we should (since it would be "composed" with human "don't know what").
If it talked a little, perhaps uttering basic sentences.... Idk. The point is that the general plot was good. The implementation wasn't. And that's the only dark spot in an otherwise amazing game. So I don't fuss much about it (and I'm really a pain in the neck for anything that isn't excellent)