The bar used to be pretty low. My father spent a few years writing and selling a system/360 time sharing system in the 70s or so. He was not a self-identified computer person, just a physics student who found a way to make a few dollars.
In the 70s and 80s and 90s so many operating systems from lisp machines to ITS to the bsds... People used to write an OS like people write frontend frameworks now.
In the 70s and 80s and 90s so many operating systems from lisp machines to ITS to the bsds... People used to write an OS like people write frontend frameworks now.