Yes. But meta programming facilities aren't stabilized for obvious reasons (it ossifies the current implementation).

Most meta programming facilities are stabilized, most importantly procedural macros.

I'm not up to date with Rust tbh. Last time I checked Rocket used proc macros which were nightly only. But maybe there is some other issue.

Most procedural macros were stabilised in 2018, but some smaller features related to them were stabilised later. Rocket also used a ton of other nightly features beyond metaprogramming, which have either been stabilised by the compiler or replaced with stable solutions by Rocket.