why does the word look "weary , stale, flat, and unprofitable" to hamlet? is his attitude youthful rebellion or a deeper wisdom

Hamlet is pretty choked up over his dad's death and his mother's quick marriage to his uncle. Hamlet has some depression going on or at the very least major melancholia. He hates it that people seem fine with this new arrangement. Hamlet is commenting on the fickleness of a world which lacks wisdom or meaning. It is a world where goodness is forgotten and lechery is rewarded. You know, if I were in a dark mood one day, I'd be inclined to agree with him!