From what I've read so far:
EC2 ASG is a simple solution to scale your server with more copies of it with a load balancer in front of the EC2 instance pool
ECS is more like Kubernetes, which is used when you need to deploy multiple services in docker containers that works with each other internally to form a service, and auto scaling is a feature of ECS itself.
Are there any differences I'm missing here? Because ECS is almost always a superior choice to go with if they work as I understand.