I think pictures alone are not the main problem at the moment, sure if you are using pictures made by other ppl without their permission then you are violating the copyrights and that alone can be a problem but the main problems are the completely stolen postings and videos. You can search for the dlike tag and almost all of them are just stolen postings. Dtube is the other problem because many videos are just stolen and they definitely didn't ask for permission.

Sadly I don't have enough power to downvote all this stolen stuff

edit: oh my girlfriend creates art videos on youtube that's why I am reacting a bit more harsh to these stolen things because it happened multiple times that some of her works got stolen.