That's like saying "the US Constitution has clearly shown it's a model that is built to last"

Sometimes bad designs stick around due to pure inertia

Unix is completely inapplicable to this environment which is inherently managed and intraprocess. Why not send an object saying what you want instead of a plain C struct, or worse a bunch of ints? How do we handle ownership across these boundaries? Why should two high level components be forced to squeeze into a primitive bottleneck between them?

Don't get me wrong: I think C is cute and fills a niche decently well. But that niche is not the one we have here.

The reasons why Unix displaced a bunch of more elegant systems were downward scalability, free distribution, and positioning to take advantage of network effects. Quality was secondary, especially with multiprocessing and networking where a lot had to change, and the designs were not always good.

It clearly hasn't, if you've been paying any attention to security. The Unix security model is that all code that a user runs is 100% trusted. That's absurd in today's world.