Have you seen ElasticBeanstalk's ECS setup? We've went 'all in' on that and it's been fairly successful for us so far. We use a combination of long-lived servers (spin up one stack which lasts for multiple versions/deployments) for our test environments, and then we do blue-green deployments for production which gives it a complete new stack for every deploy.
We've been running a bunch of services on it for a months and its been fine.
we ran fast from beanstalk to pure ecs. Security groups, rds, iam policies, if we were doing that in terraform anyway then launching an asg/elb too is pretty trivial. And problems like, for a failed deploy they were just shrug we dont know what version is deployed. And when there were failures, the beanstalk interface doesnt really tell you why, and you end up digging through random log files to find the right one. Was it a beanstalk error? ECS error? Having another layer that could go wrong just didnt make sense to us.
I'm no sure why anyone would even bother with raw esc - just let aws manage it all using beanstalk. It certainly still relies on elb/dns and whichever env vars for "discovery" stuff, but it beats rolling your own infrastructure management using ecs/cloudformation etc.
Beanstalk is great when you're at a scale that can justify one or more instances per application, but raw ECS works better when you've got lots of low traffic services that don't saturate even a single small instance.
+1 for ElasticBeanstalk Docker deployments. I looked at ECS first about a year ago and ran into a lot of the same messes the OP did. ElasticBeanstalk was way more straightforward and the CLI is pretty decent.
One thing we did run into was that very occasionally environmental variables wouldn't show up inside deployed containers so we had to bake all the application secrets into the build process. A little annoying but nothing too terrible. Otherwise everything has been pretty great.
We've been running a bunch of services on it for a months and its been fine.