I think ECS will, and should, be retired. It was a lurch in the right general direction, but ultimately missed the mark.
If you had to release a product to support the open source front runner, you did not successfully defend against it; you conceded after your tooling adoption failed.
As long as Kubernetes leads the way, lock in at any cloud provider is prevented (can even move back on-prem when the winds shift again). Kudos to Google for enabling that, but they have their own motives (ie disrupting AWS uptake).
That might be a little strong. They still have lots of other proprietary offerings you might use along with K8S. Cloudwatch, various database services, Lambda, SQS, S3, etc.
MariaDB and PostgreSQL both work well outside of RDS.
Last I saw, "pets" like databases, were not optimal in K8S either. You can make it work, but it's higher effort.
Disclaimer: I’m in risk management
I had the same experience until I created an ECS stack using CloudFormation, which made it much easier to manage.