All icons are confusing until they're burned into your memory.
How confusing they are has more to do with the complexity of the operation they symbolize than the design of the icon itself.
Naming is hard. Symbolizing is hard. Normalizing operations is not hard. I don't blame modern icons. I blame poor abstractions driven by marketing becoming the norm.
I'm waiting for designers to figure out some way to signify "save" without using a picture of a floppy disk. That was great back in the day, but I bet a large number of computer users have never seen a diskette.
People get what radio buttons are even if they never saw a radio with the mutually exclusive buttons[0] that these UI elements were inspired from - they were obsolete even back in the 80s.
Personally i never made the association until almost 2 decades after using computers with radio button elements, despite growing up having a monochrome TV that had actual "radio buttons" (or TV buttons in that case, which probably helped to avoid the association :-P).
And most people know what a phonograph/gramophone is without ever seeing one in person. I don't think a floppy icon will confuse anyone if they know it is for saving and is consistently used as the "saving icon", regardless of if they've seen a real floppy disk or not :-).
They might not be on radios any more, but round mutually-exclusive pop-up buttons are still something everyone in the modern world runs into — as, to this day, they're the idiomatic way to do speed selection on table fans.
Well, they are still called radio buttons, not fan buttons :-P.
Also i think those might be on their way out, the last fan i bought had a touch buttons (not screen) - and yeah, i often did mis-tap the button i wanted :-/
People who use cameras (dash cams, action cams, drone cameras), portable game consoles (by which I mean the Switch, yes, but also all those Shezhen "retro consoles"), and a few other things. People do still know what SD cards are, even if they don't have a slot for one on their flagship phone.
Nevertheless, the real issue is more that "saving" isn't really something you do any more; almost all apps now autosave and restore on restart, such that the real action that needs an icon isn't "save"; it's the option you get when you indicate you'd like to close an open, but unnamed project/document without quitting the application: "give this project/document a name."
Outside of the First World, that would be most people with budget Android smartphones, which normally come with limited storage and an expectation that someone who needs more can always buy a card.
How confusing they are has more to do with the complexity of the operation they symbolize than the design of the icon itself.
Naming is hard. Symbolizing is hard. Normalizing operations is not hard. I don't blame modern icons. I blame poor abstractions driven by marketing becoming the norm.