It is true that C does not protect against a class of errors related to memory safety, but it disingenuous to imply writing an OS in any other language will make it secure. At best, it will only reduce the porosity of the attack surface.

One of the reasons why Multics had a better security assessment than UNIX from DoD, was precisely how PL/I does strings and arrays.

Not wearing seatbelts and helmets doesn't save everyone, so it is worthless to use them as a vain attempt to save human lives.