When it comes to the occupation of Iraq or war in general, I don't think "Sand Castle" has much new to show or say. It's quite generic. The technical execution is impressive and the acting solid, but I can see why this ended up on Netflix instead of theaters.
Speaking of Netflix, it has to be said that they haven't hit a home run with any of their movies yet. Cary Fukunaga's "Beasts of No Nation" was pretty damn good, but most of the films I've seen have been somewhat disappointing. Maybe David Michod's "War Machine" will do the trick?