I know in GNU Guix the more Rust is used has lead to struggles in packaging and building from source for non-x86-64 architectures (demands of building the Rust toolchain, bootstrapping), e.g. [0]. With something like librsvg [1] being a very low level dependency now, Rust has become rather integral to many parts, with any changes to these libraries requiring massive rebuilds for a source-based reproducible distro like GNU Guix.
[0] https://lists.gnu.org/r/guix-devel/2021-11/msg00197.html