When Lemire writes intimate, character-focused stories, he is one of the best in the biz. When he writes mainstream superhero stuff, he just doesn't seem to have a unique voice IMO and doesn't distinguish himself from the crowd.
JLU #0 gives us a by-the-numbers team-forming comic book. I have no idea why this wasn't a #1 issue, being that it wasn't a self-contained origin story as much as it was, you know, the first issue of an arc, but hey, comics!
I read Lemire's Green Arrow which I find excellent, although I know the criticism from fans is that it's not really Green Arrow. The guy in this issue probably fits the mould better than the solo title does, but the inconsistencies between the two are pretty startling, especially given it's the same writer.
This isn't a bad comic by any means, It's just the not the type of comic that I like to read.