Out of curiosity, are you using terraform to deploy k8s, your app stack on k8s, or both?
We used K8S on a large project and I felt like it really, really wasn't necessary.
So terraform creates the cluster, DNS and VPC. Then k8s runs pretty much everything.
Mainly just kustomize piped into kube apply.
But, but, but. Having to a create a one-off database migration script imperatively.