That's part of it, yeah, lots of courses out there but they tend to be things like survey courses, etc. Some of this is that the video content turns out to be the equivalent of only a 1 or 2 credit course.
It's unfair to criticize Coursera for having survey courses if they also have deep courses, which they do. It would be nice if they had more, but that's not really a criticism.
There's a Stanford professor that has the videos from his class about the Fourier Transform on youtube, go compare that to (just about?) anything on Coursera.