Curious to know why you think so? ECS is a managed service. If Swarm was a managed service on AWS, I'd agree with you here but that's not the case.

Swarm is still brilliant for running multi-node deployments.

Mirantis purchased Docker Enterprise at a firesale price last year. They've pledged support for two years, and they say they will be "continuing to invest in active Swarm development," but the writing is probably on the wall. Their release was more excited about K8s.

Which is disappointing. Swarm is infinitely easier to setup and get running, and it scales down / uses WAY fewer resources than k8s.