I wonder who you are thinking of who 'wasted a couple of years'. Regular students do one course in operating systems. That is a series of lectures and some practical work. The practical work is a couple of weeks at most if you know what you are doing.

Some people spent a lot more time on MINIX, but that was either as a hobby or the PhD students who worked on MINIX3. But MINIX3 generated lots of papers with a best paper award, so that can hardly be seen as wasted from an academic point of view.