As a huge fan of One Piece, I'm confused by the co-worker. Are they indicating that One Piece lacks any serious overtones? because the world of One Piece is consistently shown to be a constant hell, where your only choice is whether to suffer on land at the hands of the government, or enter the endless struggle of the sea. It consistently has some of the most genuinely heartbreaking and miserable moments of any anime I've ever watched. I cry at least once an arc, typically a few times. I can't think of an anime that gets any heavier more consistently.