For me the mistake that Rust made was that it tried too hard to behave like C/C++ with its single execution stack.
Ada uses two stacks allowing a callee to return a stack-allocated arrays to the caller. Not only it allows to avoid dynamic allocations in many cases where C++ allocates memory, but it also reduces the need for pointers making the code safer even without the borrow checker.
If instead of async Rust spent efforts on implementing something like that or even allow for explicit stack control from safe code so green threads or co-routines could be implemented as a library it could be more compatible with io_uring world.
