Kubernetes is excellent, and a lot of teams adopt it about two years early.
Three signals mean it is time: you are running more than roughly fifteen services with genuinely different scaling profiles; you need multi-tenancy with hard resource isolation; or you have people who will own the platform as a product rather than a side project.
If none of those hold, managed container services do the job with a fraction of the operational surface — and migrating later is not painful, because the containers are the same containers.
The cost of adopting early is not the cluster. It is every incident for the next eighteen months having one more layer to rule out.