I've never seen any users who avoid using Rust's stdlib on principle. The closest thing is the use of the parking_lot crate over the standard Mutex types, but that's getting better over time, not worse, as the stdlib moves closer to parking_lot in both implementation and API. Other than that, there's only been one "wrong" API that needed to be deprecated with a vengeance (mem::uninitialized, replaced by mem::MaybeUninit). Especially compared to C++, the fact that Rust doesn't have a frozen ABI means it's free to improve the stdlib in ways that C++ can only dream of. While I do wish that the Rust stdlib contained some more things (e.g. a standard interface to system entropy, rather than making me pull in the getrandom crate), for what it provides the Rust stdlib is quite good.