I guess to me the colors, or lack thereof, make it feel very stark and severe for an informal/daytime situation, but the cut and untucked shirt make it too casual for a more formal situation. That aside, purely on an aesthetic basis, I think what's getting me is the untucked shirt. What kind of fabric is it? Usually shirtings don't really drape in curtain-y kind of way that are conducive to the "voluminous' kind of fit you're talking about. The fabric of the pants and jacket work better in this regard. I'm probably not articulating this well at all, but every time I come to some appreciation of the fabric and fit of the jacket and pants, the shirt makes the whole thing look sloppy instead of relaxed and reminds me of why I didn't like the photo when I first saw it.