> There was never a period of time when you could just look at any logo and know what it is
None of your examples are for built-in applications. You have to go out of your way to download those programs. You'd know what the traffic cone means because you downloaded the program with the traffic cone. You went out of your way to get it.
Let's go back to that era and look at some other built-in apps, like Pages is (these days).
Notepad: a blue-covered notepad with some lined pages visible.
Wordpad: a fountain pen writing on some lined paper. Eventually the pen disappeared but the paper remained.
Paint: a paint palette, then a bucket of art supplies, then a glass cup with paintbrushes, then back to a palette but with a brush.
Solitaire: a deck of cards.
Outlook Express: an envelope.
MSN Messenger: two people next to each other because they're communicating with each other.
Windows Movie Maker: a film reel/strip.
Internet Explorer: a big 'e' (for Explorer) with a planet-like ring around it, suggesting a planet that you could traverse. (Okay, a bit abstract)
Over the Mac, there was:
SimpleText: a pencil writing on a sheet of paper. Later re-used for TextEdit.
Sherlock: a detective's cap and magnifying glass, indicating searching. The magnifying glass was later re-used for Spotlight.
Disk First Aid: A floppy disk on the back of an ambulance.
Disk Utility: a doctor's stethoscope pressed against a hard disk.
etc.
> it was not how comprehensible logos became, but how cynical we ended up
Because, on macOS, none of the icons became any more comprehensible than before. If anything, they got less comprehensive even when the visual metaphor remained the same because the representation is so poor. That's what made everybody cynical.