I have an unpopular opinion. Non blocking IO is useful when we want to scale to lots and lots of parallel IO channels. If we don't have lots, only dozens, there is no strong need for non blocking IO. You don't actually need anything like coroutones or event driven frameworks to use non blocking IO, just loop through the sockets and tend to the ones that are ready, though event driven frameworks can make it much nicer (though still significantly more awkward than writing code in a synchronous paradigm).

Within the world of "we want non blocking IO", the world has gone crazy. JavaScript has created a whole generation of programmers who think inside out callback / yielded code is how everything should be done, and that threads are "too hard". They hardly understand the original purpose of non blocking IO and conflate the fact that they can conceptualize event driven code better than they can threads with "well that's why it's so much faster" (which usually it isn't). I can't retire fast enough from this industry.