Even when large projects might have different requirements than 'regular sized' projects, some things don't make much sense to me TBH:

What's the point of a development container when there's already Cargo which is supposed to manage dependencies? If there are any system-wide dependencies required which need to be installed outside Cargo I would consider the build system incomplete or broken?

Why is there a separate Makefile instead of using Cargo for all build tasks?

E.g. one of the great advantages of the Rust ecosystem (compared to the C/C++ or Javascript worlds) is that Rust has standard tooling. Why bring in additional tools from outside the Rust ecosystem?