If you automate everything you will never have an issue with K8, you can deploy all the required dependencies in one go. You can run the tests, if done correctly this literally requires 10 minutes.
This argument to have an LTS Version for me is like air. It's the kind of Nuclear Reactor argument. We did have the money to buy Uranium to burn but now we can't afford to dispose it normally.
Kubernetes is for flexibility not for big companies which want to use their software development processes of the 90's...
If all that holds, my question then becomes, why does your system not have a preprocesisng and postprocessong layer for compatibility? Stuff like that is easier than ever to build, and would allow your components to grow with the ecosystem?
But many interesting useful real-world systems are difficult to contain within a perfect black box. Abstractions are leaky. An API gateway, for example, cannot hide increased latency in the backend.
People accountable for technology have learned, through years of pain, not to trust changes that claim to be purely technical with no possible impact on business functionality. Hence testing, approval and cost.
More likely, you will be constrained by a patchwork quilt of contracts with customers and suppliers, or by regulatory and statutory requirements, or technology risk policies, and to get approval you’ll need to schedule end-to-end testing with a bunch of stakeholders whose incentives aren’t necessarily aligned to yours.
That all adds up to $$$, and that’s why there’s a demand for stability and LTS editions.