>I thought of that Dijsktra quote too. It sheds light on what's wrong with the OP's proposal: in return for less nesting, it worsens the conceptual gap between the program (in text) and the process (in time). A poor trade.

That's like saying that "by using FOR instead of GOTO we worsen the conceptual gap between the program (in text) and the process (in time)".

Only we don't worsen it -- we just abstract it to a level in which we can reason about it better.

Higher level is not worse -- except if you consider "more distance from what is actually happening at the CPU" as worse. Which is not: historically the higher the distance, the more programmers got done.

We don't need to keep track of the actual low level process in time -- which with callbacks we're forced to. We just need to know how the steps of the process relate. Which await and co offer in a far better form than callbacks.