To summarize: instead of improving Python's maps to consume less memory they've embedded an entirely different language, Rust, into Python to solve a particular problem.
I disagree, I think it makes Python look really good. Being an interpreted, dynamic language where most internals are represented by a hash table, it'll never compete in terms of raw speed. The people who choose Python choose it for the ecosystem and productivity, and from that perspective it's actually to its benefit that it's easy to replace your bottleneck code with a faster implementation. The only high level language in my experience easier to drop to C/C++(and now Rust) would be Lua of the luajit flavor.
Python is hard to beat for speed of development. Rust is hard to beat for performance and memory usage. So why not combine the two?
Complexity.
Complexity is a relative concern.
Out of all options we had this was probably the least conplex one given our set of tools and experience.
By Python, you mean dynamic scripting languages? Everyone already knows the tradeoff in using one of those over using a language like Rust (and vice versa). It's no surprise that Rust uses less memory. It also takes more effort to code in. What exactly is your point? That sometimes a language like Rust is the better tool? That one programming language is not the best tool in all situations?