"Powered by" is an understatement, Serde would be unusable without procedural macros. Deserializers use a ridiculously verbose visitor pattern that's completely unnecessary in a language with move semantics, it should have been a recursive descent API.

Using serde_json to accurately model existing JSON schemas is a pain because of it.

I personally find third-party deriving macros in Rust too clunky to use as soon as you need extra attributes.