Two ideas: First, you're describing exactly a traditional SFTP share with the same files being in a location but each user can have different permission levels. Also, samba shares does the same thing. Not sure if a modern web UI is a requirement for you though.
Second, you could use nextcloud and just share the files, or use groups (or circles I can't remember what they call it).
People said the same thing when cars were invented and replacing horses for transportation. It's not about fearing something new, it's about learning to use it correctly so it benefits you.