I mean, I get what he's saying because as an editor Torishima is looking at it based on their target demographic mostly. But the real issue with OP in specific is that its so long and ongoing that kids might just be too intimidated to have to read over 100 volumes
- According to Torishima, Toriyama hated manga, so he made them as synthetized as possible. But that's exactly why Dragon Ball became such a masterpiece: anyone can read it easily. One Piece, on the other hand, is too heavy and unapproachable to kids.