Humm... Most users go to Udemy for programming courses (I'm guessing, I could be wrong)
Well, that's definitely my case, and unfortunately I can't say I have finished any of the paying course I took so far. It's mainly my fault, lack of time and discipline, even if I didn't give up completely, but it's true that some courses are either too shody or too complex. It's hard to get the right balance. However, I always get answers and help from the creators, which is really helpful.
Seems a tough business for them though :-/
Some instructors are very good and spend a lot of time answering questions. Many are not and unfortunately ratings are not a good indicator to which is which.