I can't argue too much on your view of the syntax. I employ the weasel word "fine" because my experience with it is that I have little to no trouble understand

I can't argue too much on your view of the syntax. I employ the weasel word "fine" because my experience with it is that I have little to no trouble understanding and using async Rust syntax: I can read and write async Rust and conceptually grasp what is likely going on in the runtime. I have to allow that perhaps it isn't sufficient, and maybe even that this is a factor in the runtime problem. But there are other, non-syntax issues, such as synchronization primitives, IO events, etc. that are clearly underspecified. No maybes about it.