I think moocs are usefull to jump start you but after that you need to do more. I studied CS and did find the deeplearning.ai course helpful in getting started. Without it much of the ML content was not easy to grokk. But now that I"ve gone through that I get the gist of what papers are talking about. After you do a MOOC though you have to continue with doing real work as in exercises, Kaggle competitions and just playing with things.