What? Incomprehensible muck. Look, I've read the original Middle English poem, it's one of the great works of English lit, but what the heck is this movie doing? Most of the dialogue is incomprehensible (because it's mumbled and hissed and reverbed and badly recorded, not from the diverse accents - almost none of which make sense for either England or the period). It's set in the Middle Ages, so of course we have the clichéd ubiquitous mud and darkness - there's almost no color in this thing, the Green Knight is grey-black (hello, he's the Green Knight, symbol of rebirth in winter, why is that so hard to figure out?), most of the scenes are so dark I can't even make out what's going on. Believe it or not, the Middle Ages were not all mud and darkness! People wore brightly colored clothing! Plants grew! The sun shone! (Note: Neither was the world sepia-toned before 1990, for any filmmakers out there.) I was really hoping they would treat this great story with respect, but it's just another uncomprehending, incomprehensible, pretentious, slow as molasses muddle.
BTW, there's a nice school opera based on the poem, by Richard Blackford. It actually sticks to the story and offers some lovely music. And it runs less than an hour.