Well, to begin with, I think people worry too much about vendor lock-in. Use the tools your cloud vendor provides to make your life easier. Isn’t that one of the reasons you chose them?
That said, moving containers to another container orchestrator isn’t terribly difficult, so I don’t personally worry about vendor lock-in for containerized workloads. If your workloads have dependencies on other vendor-specific services, that’s a different story, but basically a container is easy to move elsewhere.