Async rust currently isn't well-designed for pushing throughput to its limits, though. You really need a lot of batching and very few uses of atomic ops on your CPU to get to extreme throughputs, and Tokio doesn't generally give you great batching. I have also found that good concurrent data structures for Rust are a lot harder to find than other languages.
Stock Tokio is tuned towards the general set of applications, attempting to make things work well out of the box, while being ergonomic to use. But, this isn't set in stone. There are knobs and patterns that can be used to really squeeze out performance, as seen with Actix Web, which is based on Tokio [1].
I'm not sure why you can't make a framework tuned towards a "general set" of applications that offers batching and run-to-completion semantics. As far as I can tell, the biggest problem with this is the semantics: async/await and futures models of async programming make it hard to figure out how to produce batches.
