I've hemmed and hawed over this as well, but I believe that sometimes software can be complete and stable and not need constant iteration. As long as they add security patches and don't remove it from Docker, I'll still default to Swarm.

My fallback, if Swarm is ever removed, is Hashicorp's Nomad. I've only used it in a hobby capacity, but is (at face value, at least) another wonderful piece of software. I've used k8s a bunch in production (including right now at my current employer) and just can't recommend it – it's a technical distraction for most teams.