At this point, there is probably nothing that can rescue either Microsoft or Linux from the hordes at the wall. Both are performance-first operating systems. There's nothing surprising or unusual about that; this is the dominant paradigm. Windows NT made at least some attempt in the other direction until version 4, but then they prioritized UI latency over memory security. LLMs apparently don't have to be able to think to recognize patterns which indicate vulnerabilities. If having closed source is even still a benefit in hiding failures, it won't be for long.
On top of that, the hardware isn't secure enough either and both are going to have to be addressed to reasonably secure our systems from this new threat. They were never really secure, humans could find the same vulnerabilities, but there weren't enough humans looking. There's lots of compute hours being spent looking.
This isn't limited to Windows and Linux, every vaguely common system has the same problem. None of them were built for security first, because such a system would cost more to operate and almost nobody has been demanding to pay more for less performance in security's name. But many have long predicted we'd get to the point where we start to spend our performance advancement budget on security because some development will necessitate it, and it seems like we might have arrived there now. There are and have been more secure systems, but the home PC is going to have to become one of them because otherwise we won't be able to use them for anything other than getting pwned.
