I think one of the problems with sites like this in general is that the market is flooded with low-quality product with nothing but the reputation of the person

I think one of the problems with sites like this in general is that the market is flooded with low-quality product with nothing but the reputation of the person teaching the course to go by. It's probably one of the reasons that university systems have accreditation organizations, so that courses and degree programs are forced to meet a set of standards. Specifically for self study programs, there's not enough instruction time spent on tying everything together in a course. Most of them just bounce from topic to topic and then you're done. In certain "certificate" programs, they'll have some sort of capstone project, which still isn't the same as getting additional educational reinforcement, which I feel is probably needed MORE in self-study systems than in university settings where you can get office hours and discuss topics in-person with classmates.