Its not that listeners don't want or care about positivity, its just that listeners don't want to feel as if they're being preached to. Listeners want positivity they can relate to presented in a way they can relate to.
One of the biggest songs of last year had a very positive message
You could disagree, but then you'd be disagreeing with the idea of unwavering loyalty, which is what the song is about. Is loyalty not something people should celebrate in song?