Exactly. Why should e.g. a floppy disk symbol signify anything to anybody born after 2000.
The Apple II was the first computer that was widespread enough for people to have seen that had a floppy disk. It came out in 1977. Apple dropped the floppy disk in 1998 (21 years later), so it's been 22 years since it was standard in Macs.
Even allowing for some switching time, it has meant "save" for longer than it was a common physical object.
But if i really have to come up with something, I'd say green arrow pointing up. Meaning 'upload to your (own private) cloud'