Poop because manga offers no value ( isekai, harem, NTR e.g. cuckolding, gender swap, living on MMORPG ). Old man is technically correct.
I know you're joking, but I still have to disagree with you, except for NTR and cuckolding.
A good manga generally has a theme, a lesson it wants to convey to you. Take One Piece, for example. I mean, it's a bunch of pirates fighting against other pirates and the world's government, yet it conveys the value of friendship and teaches us that corruption can happen even at the top.
Yea, it's generic, but many stories convey meaning, you just have to try and find it.