You pay for the window seat, you have control over the window-blind, in my opinion. Apart from T/O and Landing of course where it should be open for reasons discussed before.
Don't complain and make the poor window seat people who paid to look out the window at the beautiful landforms and admire the engineering of the aircraft's powerplant/wing suffer and sit in darkness when the problem can be solved so easily:
a) Eyemask. Its either given away free in an amenity pack or you can get one for a couple of pounds, tops.
b) Improvise! If you don't have a) then you are bound to still have a jacket/sweatshirt/hoodie that you could use to cover your head/eyes.