Everyone decided that "save" = "disk"
Maybe a different looking disk, but still a disk.
That universality across apps for basic functionality was the biggest feature: it didn't matter if I knew what a disk was or not, because I knew the disk-shaped thing meant save in every app.
The original modern sin of UX was having the hubris to ditch universality because they believed whatever batshit they dreamed up was better enough to justify doing so.
It wasn't. Arguably, it couldn't ever be.
You could come up with a unique wiz-bang UX for something that's objectively 25% better than skeuomorphism, and it still wouldn't be a net improvement. Because no user cares about one specific app enough to train on it.
But building a hammer that looks like every other hammer doesn't get you on the cover of design/UX magazines...