The key difference for me is that the PSTN moves at a snail’s pace, maybe because of regulatory entanglements, maybe because of interoperability constraints. The result is that problems which have been rampant for decades — spoofing, spam, robocalls — remain trivial to exploit. Email has plenty of its own problems here, but at least you get more signals to work with (headers, DKIM/SPF/DMARC, filtering, etc.) than just a string of 10–12 digits with no real context.
That’s why I’m less inclined to “cherish” a system whose shortcomings shift so much burden onto the end user’s well-being, all in the name of interoperability. If interoperability means putting up with abuse at this scale, then that interoperability isn’t worth much — and that’s where my frustration comes from.