It's not, really.
^This is more akin to actual constructive criticism, while this:
...Is more of a pejorative. It belittles more than it does constructively criticize.
Constructive criticism respectfully points out flaws in a work while also suggesting improvements to said flaws. That's the definition I've been taught, at least.
Back to the MOC, however; @Toa_Radrix as others have said, I find it to be a little thin/bare. Bulking up the limbs and chest, as well as giving it more unique armor pieces, might help with that.
The mask looks cool; is it custom-painted?