Okay, yeah, that is fair. I have written enough raw futures in anger to be like "it's not practically possible", but you're also right that it is actually practically possible, regardless.
Oh, practical is also separate from my answer, since my reading of the question was strictly "theoretical". ;)
Maybe about a decade ago I wrote a raw futures system for async asset loading off DVDs on the Nintendo Wii in C++, and it had to play nice with the real-time rendering system. I didn't stand back far enough to abstract it the way futures work today, and as a result it was an absolutely awful experience. It was so difficult to understand and debug, I dug myself an enormous hole. Having used futures in JavaScript and Scala and other languages since, I'm certain having real futures would have saved me months of crunching.
I would agree that await syntax brings a huge degree of practicality to what was previously theoretically possible.
