I think a lot of people are stuck with C++ due to the fact that there are a lot of legacy C++ codebases (many decades old), moreso than legacy Python or Javascript codebases.

Rust does a ton of things better than C++ as other people here are mentioning. For example, at my 20-man C++ shop, we have around 2 people's worth of full-time cmake work, that is, just maintaining the build system. This work would largely go away if it was a Rust codebase.