I (roughly) believe this as well[0], but more flexibility generally means more complexity. Right now, if you don't need the flexibility that k8s offers, it's probably better to use a solution with less flexibility and therefore less complexity. Maybe in a decade if k8s has eaten the world there'll be simple k8s-based solutions to most problems, but right now that's not always the case

[0] I think that in the same way that operating systems abstract physical hardware, memory management, process management, etc, k8s abstracts storage, network, compute resources, etc