I think callbacks do not scale with large projects as they make understanding the flow difficult (at least from my experience of multi million LOC code bases ba

I think callbacks do not scale with large projects as they make understanding the flow difficult (at least from my experience of multi million LOC code bases based on callbacks that called callbacks). Using callbacks in Rust is not idiomatic, at least I haven't seen such code over the last two years writing Rust, and Rust syntax and semantics with life times is not tailored toward that approach. So the author forces an async style on Rust that it was not build for and then complaints.