Think that youtube have useful things but it have a lot of crap. Not only poor quality video. Have a lot of popular low brain youtubers who are popular only by use bots and be kind with a pretty face. But there are some content protected by copyright that can´t be founded in others websites and in youtube is for free. I know is bad but i don´t have money for buy some educational videos. Have a nice weekend due and congratulations. You are doing great.