Honestly with Fable I think anyone is going to be able to reverse engineer a desktop app and get the coding agent to automate it.
The Codex computer use functionality actually uses OS level accessibility trees, so thats also possible without screenshots.
I can't tell if you're saying that you think every native app in the world can be vibe-replaced with a web app (they can't) or if you're saying it will be easy to vibe-code a reverse-engineered replacement for every native app (you can't)