It's honestly not that hard for a random iOS dev to learn the macOS ropes, the principles and paradigms between UIKit and AppKit are the same and at this point both frameworks have a comparable amount of baggage and quirks. AppKit adds some complexity in some areas (window management comes to mind, which UIKit has now but no one bothers with) but helps in others (document management is still miles ahead of UIKit's).

The problem is convincing someone to try. There's a reputational issue "AppKit is haaaaard" "AppKit is baaaaad" "AppKit is dyiiiiiing". There's also a career issue as it's felt that building native mac apps is a career dead end.