It gets complex with ACLs for permissions, lifecycle controls, header controls and a bunch of other features that are needed on S3 scale but not at smaller prov

It gets complex with ACLs for permissions, lifecycle controls, header controls and a bunch of other features that are needed on S3 scale but not at smaller provider scale. And many S3-compatible alternatives (probably most but the big ones like Ceph) don't implement all of the features. For example for lifecycles backblaze have completely different JSON syntax