--Darkened abilities either don't meet the requirements (for example forgetting to equip the wrench on the mechanic for the wrench throw) or they are supposed to be used on the field, out of combat
--From my experience, 95% of the time enemies avoided traps (even bear traps) and if the passage was too tight and only 1 tile wide, they would stop moving altogether. Orange said this is not intended so it's kinda creepy. I noticed that if they are far when you palce the trap, it's more likely they will walk over it.
-- When all items have "use" grayed out, closing the application altogether and restarting the game fixed for me. It only happened once to me.