Glasnostic CEO here. These are all valid points and good, straightforward ways of doing things in a perfectly engineered world, where they work until they don't.
Problem is, our world is rarely perfectly engineered. Our perfectly engineered application becomes a service to other applications. Some other team deploys something that affects our dependencies. An external partner hammers our API. Our managed service provider has an issue. Noisy neighbors cause shock waves, gray failures compound. These things happen irrespective of whether your code is correct or not.
Unless your service architecture is small, "perfectly engineered" is an anti-pattern because it is too expensive to track down and code against such events, no matter whether we run in Kubernetes/Istio or elsewhere. Operational challenges always require operators.