security so advanced that an individual software author cannot write a small MacOSX app, add an About box and cool icon, and distribute it themselves, as they choose?
Assuming by "as they choose" you mean without buying a Developer ID then yes, they can do these things. In fact if you don't supply signing certificates Conveyor will self-sign your app and produce an HTML download page with instructions telling the user how to bypass GateKeeper. It'll also generate a `curl | bash` one liner to install it from the terminal. Obviously, this isn't meant for consumer software. Really you shouldn't bypass GateKeeper even if you're a pro level developer, although of course in reality we all do it.
I too used to be maximally skeptical about this stuff. I saw what Apple did with iOS and like so many others saw the writing on the wall. But it's been 15 years now and you can still distribute and run unsigned Mac software if you want to. Developer ID/notarization remains very different to app review. App sandboxing remains optional. You can still get root if you want, both the default de-privileged version and the full fat version (by disabling SIP).
In the end the wall writing existed only in our minds. Apple have never closed the macOS platform like with iOS, and honestly I see no sign they ever will.
