IIRC Rust by default brings in a few things (panic handling is the main one, and also jemalloc) that make its runtime larger than C (but not larger than C++), but they can be disabled with compile flags. Many folks do, for embedded stuff.

Rust also lets you write a custom runtime by specifying a start function if you want.

> The fact that it's design is not very stable is also a problem.

Rust is stable.