Your points mostly only matter if you're running on bare metal. If you're in the cloud then you've got load balancers and databases covered by your cloud provider. I need Kubernetes to handle problems that I already have great solutions for. I want it to handle the problems that my cloud provider provides poor or very specialized (ie: lock in) solutions for. Which for me it does very well and a lot more easily than doing so without Kubernetes.
edit: Kubernetes secrets are also either good enough (ie: on par with Heroku) or your cloud provider has an actual proper KMS.
edit: Kubernetes secrets are also either good enough (ie: on par with Heroku) or your cloud provider has an actual proper KMS.