Earlier quoted context omitted.
I guess you could make the case that windows is written in C++, which is a superset of C which was designed while writing UNIX. Sure the OS is different, but it ended up being built from the same blocks. If we didn't have C, would we have Windows as it is today?
Looking back at what Xerox PARC and ETHZ were doing with their workstations, maybe that wouldn't have been much of an issue.
Pascal was not bad at that role, and it would have been possible to develop all the code which was eventually written in C in Pascal too. At least in the dialects that weren’t made just for education.