Minicomputer operating systems like Unix (later to include Linux), VMS, RSX, RSTS and mainframe operating systems like MVS were generally designed sufficiently well (in the context of suitability for general purpose) not to have to reinvent them. But if there were only Windows, then yes, I would be forced to reinvent the operating system as part of the project plan.

Only two base protocols are used by browsers, but there are plenty more that had to be created for more specific purposes like mailservers or indeed tty. It would hardly be reinventing the wheel then if for example and hold it hold it I only say for example, I were to create a ttys for tty just as there is an https for http.