I'd say it's more of an opinionated approach to a web framework, which reduces boilerplate on a lot of simpler applications. In order to facilitate this, it ends up creating more of a Domain Specific Language (DSL) using macros and types for Rocket, which can be harder to manipulate in ways you might expect as a Rust developer.

Axum on the other hand tends to avoid macros and uses the type system in "more composable" way with other Rust crates, and while still providing a concise way to create web apps, has resulted in more boilerplate to hit the ground running in my experience.