Containerd's advent makes things simpler for projects like Kubernetes to get their hands on the low-level "Docker" components they require. Rather than using Docker directly, they have a far more user-friendly interface to the container runtime. Because container technology is now standardised by the OCI, alternative runtimes can be utilised as well. So, Docker may be getting phased out.
Docker is a collection of technologies for dealing with containers. A container runtime such as containerd is an example. A container runtime is a mechanism that handles the creation, execution, and destruction of containers. Containerd is the runtime used by Docker.
Docker Desktop contains a Kubernetes server and client that operates on your machine along with Docker CLI integration.
Docker is being phased out in favour of runtimes that use CRI, which was built for Kubernetes. Images developed by Docker will keep functioning as it used to with all runtimes.
If you're a Kubernetes end-user, you won't notice much of a difference. This does not imply that Docker is dead, or that you can't or shouldn't use it as a development platform any longer. Docker is still a helpful tool for creating containers, and the images generated by docker build can be used in your Kubernetes cluster.