The project that will replace Kubernetes will be something that provides builtins that compose together to EXTEND the system. With such a foundation, you'll be given the flexibility to evolve over time and correct design flaws. Kubernetes was in a rush to beat competitors out in the early orchestration wars, so they focused on primitives that people needed to deploy "today". I think they did a good job, but the focus wasn't on extensibility.
In an ideal world (and I've proposed), there be a long term SIG/WG that experimented with custom controllers to add new primitives that focused on EXTENDING Kubernetes. Most companies at the time wanted to tighten up the core APIs, not realizing that they should be skating towards where the puck is going. Now every major Kubernetes provider is past the point of just getting clusters into folks' hands and are realizing they need to add more functionality, but have no means that doesn't come at the cost of explosive complexity.