Title is misleading. k3s is a deployment stack/distribution that builds off various Kubernetes modules. It must pass a certain test suite to conform to Kubernetes standards.
What you might be trying to compare is kubeadm which is the official deployment stack provided by Kubernetes.
im not trying to compare it with kubeadm (which is a more a setup script https://kubernetes.io/docs/reference/setup-tools/kubeadm/ ) but with the fact that vanilla kubernetes comes with moving parts that have to be configured and maintained and also updated separately.
you can actually setup "kubernetes" which is often referred to as vanilla kubernetes without it too. See "Kubernetes the hard way" by kelsey hightower.
What you might be trying to compare is kubeadm which is the official deployment stack provided by Kubernetes.