most of the courses on coursera are for uninitiated and have very shallow content (there are some rare exception). So if you like you can search for a good book or some video lecture from good university. like this is for statistical learning "https://online.stanford.edu/courses/sohs-ystatslearning-stat...
I think you are generalising too much, there are also some good courses on Coursera. But many are more shallow than e.g. EdX, which has some excellent more in depth courses.
That's true. I think most of the recent courses from John Hopkins university illustrate this the best. They even have a separate course for Linear Regression!
However, if you spend enough time sifting through the junk, there are some decent material.
