I just looked through Maguire's gallery on the DC Comics database and it definitely does not strike me as dark and gritty. It does make one wonder what exactly they were thinking when they hired him. If you want dark and gritty, you hire someone who does dark and gritty art, it's not that hard to figure out.
Giffen, DeMatteis and Maguire had a big hit with Justice League back in the late 1980s. Trying to capture lightning in a bottle again.