One Piece YouTubers have a base that they need to appeal to. Click bait titles, over reactionary phrasing and gratuitous praise is what their audience eats up.
It must work or all these folk wouldn't do it. Ultimately these guys value their ability to make money. What else are they gonna do? Tell their audience that this series is in fact shit and that they shouldn't watch it? Cause I'm pretty sure if folk are put off One Piece then they ain't gonna spare time for a YouTube channel that is nothing but One Piece content, like most of these channels are.
No audience, no money. Simple as.
Not going to lie, this is kinda funny.