I am not European so I do not know the details or the processes used in drafting and implementing this legislation or its implementation. That said I am greatly affected by its consequences on this site. This has to do with the age of the users at time of their posts? Or opt-in language or what?
I just don't see how laws can be applied retroactively to historical material. Surely EU regs didn't intend that? Especially since most likely a huge percentage of the people who were underage at the time are over age now. Can you imagine if YouTube removes all of its videos produced by underage creators? What would happen to Minecraft videos then?
You can read about the law online by searching for "GDPR". The law is comprehensive and covers all aspects of collecting, using and managing user data. A fundamental component of this law is consent, meaning data collectors must obtain consent for a wide variety of actions, including the transfer of data. That means to be compliant with the law we were obligated to obtain consent from every user in the European Economic Area to transfer their data. Many users did not provide their consent and as a consequence we were not legally allowed to transfer their data. This was an intended consequence of the legislation. YouTube would have to go through the same process if it were sold.