Tried ACL, it kind of works. However users first respect the creation umask, which is generally 022. Which means they can create files in my directory but I can not delete them.

You can force everyone working with you to set their umask to 000, which clearly is not a really nice solution. However, even this does not solve the problem, since if they copy anything over which does not have 666 permissions then you can not edit it or delete it.

Then you’re stuck with a bunch of files by someone else who left you their things that you can not delete.

I still have 1 TB of stuff somewhere from a user which has long been deleted from the system, I have no other way to delete that stuff than contact the system administrator.

You can assign a group and then set permissions to 660 and do some ACL magic which hopefully works to enforce a umask of 0 on group; however you can not create a group without being root, which does not really solve the problem.

To be fair, I would appreciate if users were allowed to create their own groups.