What is it that interests you in the directory? What kind of application are you thinking of?
I have often thought about the reviewing and versioning aspects of the directory as useful features for sharing pedagogic projects among students (drawings, compositions, coding projects, speech recordings, essay drafts, etc.). or teaching content among instructors (lesson plans, printed textbooks/booklets, orientation guides).
I agree we should not duplicate a Moodle-community Plugins directory, but there may be other uses of the directory that are currently not handled by the database module.