For when setting up a kube cluster is too time consuming and you still need basic clustering.

We use docker swarm at work. We have 0 issues with it.

I do for a small home pi cluster

I do!

Kubernetes is a nightmare and overkill for most things we need to run, and Docker Swarm is super easy to setup and maintain.

We only use it for one application, though. The app needs to scale horizontally and scale up and down with demand, so I put together a 6 node swarm cluster just for it. Works great, though the auto scaling required some helper scripting.