You must be aware that ACLs are well supported by all major UNIX operating systems (yes, Linux is UNIX, there are/were two general-purpose Linux distributions c

You must be aware that ACLs are well supported by all major UNIX operating systems (yes, Linux is UNIX, there are/were two general-purpose Linux distributions certified as UNIX). It's just that basically nobody is using them because they're rarely necessary, and there are easier ways to implement access control if you want something simpler, and also far more powerful mechanisms for when that's needed.