Now imagine operating system, that has no directories (and no path separators) or no filesystem at all.

Like CP/M, DOS v1, RT-11 etc.

VMS used:

    node::device:[dir1.dir2.dir3]filename.extension;version
from memory, you could have up to 15 nested directories.

The versioning was cool as long as you remembered to clean them up.

Or even just Amazon S3.