Udemy, Skillshare and Coursera have failed to create a product which attracts me, and the general population. Their focus on specific content and consumption habits is both a blessing and a curse, depending on who you ask.
After a while, the algorithm aligns somewhat anyway and you occasionally get a good recommendation from the front page or related videos. But first, you have to curate your tastes so that it knows what to pull.
I could generalize your comment to say that the world wide web itself contains a vast repository of useless or malicious content and is a dangerous pipeline to extremism. But we find corners of it that don't facilitate toxic content, and we ensure the livelihood of those who produce useful things for us. They benefit from a narrowcasting service with a large audience and ad network such as YouTube. Until one of us can provide them a better service, that's what they're stuck with.