Khan academy’s material is mostly useless to me, as someone who has gone through high school and college taking a wide variety of courses, and read up on the basics of many fields; I could probably get something from the finance and organic chemistry sections, if I decided those were important to learn about (though I think I’d start with a book or a set of university lecture videos first).

MIT’s OCW by contrast is a gold mine.

The two are just aimed at entirely different audiences.