Here's some of my personal complaints. I don't in general know how to fix them.
proc_macros need their own crate
generics cause problems. Many useful macros can't handle them. Try using a generic that's a complex async function, then pass a closure to it.
There's this kind of weird mismatch where sometimes you want an enum wrapping various types, and in others generics. I find my data flows switching back and forth.
async in rust is actually really good, but go does it better. I don't think rust could match go without becoming a different language.
Traits are just a big mess. Trait implementations with generics have to be mutually exclusive, but there aren't any good tools to make them so. The orphaned trait rule is necessary to keep the language sane but is incredibly restricting. Just today I find certain a attribute macros for impls that doesn't work on trait impls. I guess I have to write wrappers for every trait method.
The "new type" pattern. Ugh. Just make something like a type alias that creates a distinct type. This one's probably easy to fix.
Cargo is truly great, but it's a mystery to me right now how I'm going to get it to work with certain packaging systems.
To me, Rust is a bunch of great pieces that don't fit together well.
I use a chainsaw maybe two hours a year. Same with my neighbors, yet each of us owns a chainsaw.