Symbols are hard. They can be done well. I don't think many would mind changing a 'call' button with a '[telephone receiver icon]' button, but those kinds of examples are probably in the minority.
It’s weird because no one has a phone that looks that way now. Does the younger generation even know that it’s a phone? Same with a lot of software iconography.
I don't think it's much worse than having an icon of mobile phone from 90s with a grid of buttons and external antenna. Almost no one is using those either. And a featureless rectangle with rounded corners in the shape of modern smartphone doesn't make a good icon. The best you can do is rectangle with circle for pre iphone X style home button or more generic slots for speaker/microphone which still makes a bad icon and are going away.
Having an icon of smartphone in a smartphone for the call app wouldn't be very helpful. And considering modern usage a smartphone doesn't even a have a strong association with calling.
I mean, I knew how a rotary dial worked (from a UX perspective) just through watching films before I ever got to handle one (and I've never placed a real call with one), so I'd assume that gen Z and A can still recognise a ye olde phone, assuming its not one with some wild design that's on the edge of the (Graham) bell curve of what constitutes a normal 'phone' shape.
Even then, most call icons I've seen don't only have the receiver as part of the icon, but some waves to, to indicate sound (speaker/sound icons often do the same, unless intend to mean 'mute', but that's usually paired with a cross or something). Given that, you could probably get away with anything half-moon-ish shaped, so long as it also has those waves on the upper end of the icon, and it'd still be recognisable as a phone receiver and a 'call' icon (please don't do that though. Just make a normal icon).
It’s weird because no one has a phone that looks that way now. Does the younger generation even know that it’s a phone? Same with a lot of software iconography.