Well for one, and this is a big one, many games implement specific features such as character progression, rewards and even loot boxes that are specifically made to keep you playing. They directly trigger dopamine reward centers in the brain and are very much tied to addiction. Loot boxes especially are literally just gambling.

Youtube kids is also all kinds of messed up. Videos created using algorithms specifically to draw the attention of kids and sometimes contain very disturbing images and themes.

This article is a good overview of how Youtube is not a good choice for kids: https://www.theguardian.com/technology/2018/jun/17/peppa-pig...

Here is a video on Jake Paul (and many big youtubers) and how he markets HARD to kids while also having videos containing very inappropriate material: https://www.youtube.com/watch?v=ywcY8TvES6c

On top of this, in terms of TV/Youtube vs books, there is a big difference in terms of it's effect on language, communication, and development. Also, TV/Youtube is a passive form of learning, reading books is active:

https://www.huffpost.com/entry/books-vs-tv-how-they-stac_b_1...