If you only need zero downtime deployments, compose and traefik/caddy are enough.

If you need to replicate storage, share networks and otherwise share resources across multiple hosts, kubernetes is better suited.

But you'll also have much less control with compose, e.g. no limiting of egress/ingress and more.

As I see it, managed Kubernetes basically gives me the same abstraction I’d have with Compose, except that I can add nodes easily, have some nice observability through GKE, etc. Compose might be simpler if I were running the cluster myself, but because GKE takes care of that, it’s one less thing that I have to do.