Practically speaking, all of it. The prolonged effects of handing an iDevice are damaging to their psyche. Kids aren't in a position to exercise rational decisions on what is and isn't acceptable content. The Youtube for Kids content filtering isn't nearly as advanced as it should be, so parents end up spending an inconsiderable amount of time attempting to filter to no success. These videos, along with those "Daddy finger" songs, adults unwrapping toys and "Ryan's toy review" where the little brat gets all the toys and destroys them are mind-numbingly pointless and damaging (considering the lack of value). At some point, parents need to consider the unknown factors and the possibility of (incidental) trauma.
At least, that's the conclusion I've come to after watching my four-year-old consume some of the above. Counter to that, the reduction of screen time has turned her more empathetic toward her sibling, though I can only state that qualitatively.
Did you watch the video where a series of marvel heroes were captured and buried up to their necks in sand? These videos are nightmare fuel for children.
Yes. Block it. Turn it off. Try handing them crayons and paper. YTKids is a product begging for your time and attention and that of your kids. It sucks and beyond that may be damaging so stop buying it (with your kid’s attention). Turn it off.
Never let your kids browse the open internet without supervision. Create curated playlists that they can watch when you aren't able to devote 100% of your time to their supervision but still want to occupy their time with videos
Block. If not, then filter the content though I can tell you their content blocking algo is terrible at blocking new content so you end up in a game of cat & mouse.
I think the author's implication is the 'wrongness' is the development of an ecosystem which encourages the creation of sadistic content marketed to children.
At least, that's the conclusion I've come to after watching my four-year-old consume some of the above. Counter to that, the reduction of screen time has turned her more empathetic toward her sibling, though I can only state that qualitatively.