The courses are usually worthless money grabs. A lot of these so called expert traders have been called out on their scammy tactics of selling "courses". Some of them have even received cease and desists and sometimes entire lawsuits have been thrown at them for financial advice that lost people a lot of money. That just goes to show you can't trust youtubers and influencers.... And just because they say "this is not financial advice" in their videos, does not make it actually not financial advice....
Some people learn the hard way.

I wouldn't say "all". I mean there are so many bad ones that it would take a lot of time and expertise to find the really good ones and if a newbie is trying to learn than they wouldn't really know which one is the better one right?
So, I agree that a newbie should be staying away from paying courses, if there is a free youtube one then it wouldn't hurt, well it would if it teaches something wrong but I doubt something with millions of views and a ton of comments could be too bad. If you can find cheap or free ones then just go with them, there are some paid and amazing ones but finding them would be a big pain and wouldn't really worth it.