I'm a completely self taught outdoor climber (with the exception of a lead belay course indoors) and have worked up to some pretty advanced stuff. Trad, big wall, self-rescue, etc.
Youtube was a big part of that. You can watch videos published by authoritative sources, cross reference them with books, etc. and get a very good understanding of a topic. Even when your life is on the line.
Then you can start branching out once you know the building blocks. Some rando on Youtube is showing you how to build some new-to-you self-equalizing anchor? Well they're just using the knots and concepts you already know from the authoritative sources. You can verify it's safe yourself, and then judge the usefulness.
But I've seen my fair share of people setting up american death triangle or threading ropes directly through the metal anchor. I've seen people using daisy chains as personal anchor device or taking hands off the grigri.
I fall on the side of holding people back is better - but who knows, maybe not
Do you think these people have spent even a second doing any actual research on Youtube or otherwise, though? I have a hard time believing there are any Youtube videos suggesting the use of the American Death Triangle or threading ropes through the fixed anchor chains. Not using a daisy chain as a personal anchor is basically a meme at this point in any climbing forums.
In that case, it seems like the real thing to suggest is that people not just go out there and wing it. It's not that Youtube has failed them in that case, it's that they didn't even use it.
But of course you should take actual lessons from instructors before using youtube as a resource.