The Apple Developer Program is only needed for macOS if you want to do sign your binaries or distribute through the Mac App Store. And you only have to pay Microsoft if you want to publish to the Microsoft Store (or use Visual Studio if you're a company that has more than 5 Visual Studio users, more than 250 computers, or more than $1 Million USD in annual revenue).
> buy certificates for signing binaries
Fair (though both Windows and macOS will run apps that haven't been signed, with more warnings of course).
> share 30% of my revenue with them for barely any reason
Only if you use their stores (Mac App Store or Microsoft Store), and it looks like the Microsoft Store won't take any cut if you do your own payments and it's not a game.