It's "Amazon ECS", and it works pretty well for standard fare CRUD web services, but more complex use cases quickly end up pulling in more and more AWS services (for example, if you need to run a cron job, you can use EventBridge to trigger an ECS task or just do it all with Lambda). This isn't dramatically worse--it's mostly just different. Kubernetes APIs are more consistent than in AWS, and Kubernetes tends to be more flexible and less limited than AWS. It's also much easier to extend Kubernetes or find a pre-existing extension than in AWS. But mostly it's not going to make or break your project one way or the other.

If you're just running CRUD web services, this is fine, but if you need to spin up a background job or do more complex orchestration then it can quickly become advantageous to