On top of that, it's either the OCI spec that's broken or it's just AWS being nuts, but unlike GitLab and Nexus, AWS ECR doesn't support automatically creating folders (e.g. "<acctid>.dkr.ecr.<region>.amazonaws.com/foo/bar/baz:tag"), it can only do flat storage and either have seriously long image names or tags.
Yes you can theoretically create a repository object in ECR in Terraform to mimic that behavior, but it sucks in pipelines where the result image path is dynamic - you need to give more privileges to the IAM role of the CI pipeline than I'm comfortable with, not to mention that I don't like any AWS resources managed outside of the central Terraform repository.
[1] https://stackoverflow.com/questions/64232268/storing-images-...