This manifesto is made just for you! Waiting for the response before updating the screen is the wrong answer. It’s not impossible, you’re assuming incorrectly that the manifesto is saying the final result needs to be on screen. It didn’t say that, it said the app needs to respond to action visually, not that the response or interaction sequence must be completed within that time frame.

The right answer for web and networked applications is to update the screen with UI that acknowledges the user action and shows the user that the result is pending. Ideally, progress is visible, but that’s tangential to the point of the manifesto.

A client can, in fact, almost always respond to actions within these time constraints. The point is to do something, rather than wait for the network response.