This is only touched on in passing, but I think editing is the real missing link here. When content was gatekept by publishers of various sorts, they wouldn't let anyone just ramble on for as long as they felt like. When anyone can do it with no constraints, well, a lot of it is going to be crap.

Producing good work is hard, and part of what makes it hard is not the production of "raw material" but the cutting down of the bad parts and the distillation of the good parts into a more concentrated form.

When I was in college I took a class where we had to write a weekly one-page summary of that week's readings/research. It was much harder than it would have been had there been no length limit. It's easier to make a three-hour podcast than to make a one-hour podcast.