K8s gives us declarative infrastructure with eventual reconciliation. That's massive, and there's nothing else around that really does that.
I have a hard time taking anyone sesriously that makes the case that k8s is bad that hasn't fully grokked the above.
One is for making it easier to manage large, complex infrastructure. The other is as a quasi-OS for containerized software.
Instead of using a new technology to move infrastructure complexity away from developers we now run development environments on k8s, piling even more complexity and layers of abstraction on.
Not sure what you mean by declarative infrastructure but eventual reconciliation has been implemented in at least one other project (now retired) called Apache Aurora[1] which runs on Apache Mesos[2].
Twitter ran (and probably still runs) a combo of these to huge scale and great success so I don't think it's fair to say that there's nothing else around that does that :).
K8s is great, but we should be careful not to rewrite history.
“Under the radar” comes a new generation of better systems and components that learns from these learning vehicles of computing and will change how we deliver services fundamentally, but without k8s and Linux we would never have gotten there. Open source RISC-V co-evolved with seL4, WASI, webassembly and NATS comes to mind, but I’m sure the future will take its own path.