There's a lot more to Kubernetes than avoiding lock in. Pick your favorite managed provider (GKE?) and stick with it. Use all of the GCP native tooling also so that Google can manage your network ingress and load balancers, TLS certs, etc. You are 100% right that there's still lock in.

But Kubernetes does more than avoiding lock in. Kubernetes creates a common interface so that if you chose GCP and I choose AWS and someone else likes DigitalOcean, we can all benefit from using the same tools across the stack. Very few tools on the linked landscape graphic are specific to a single provider.

If you choose Kubernetes solely to avoid vendor lock in, then you should reconsider. But if you choose it so that you can easily use any of the tools on this landscape, regardless of where you are hosting your cluster, that's a little different and has a lot more value.