It’s worth noting that C++ templates themselves are a purely functional language, and a Turing complete one at that

Feature parity with C++ is not a goal and neither should it be.

I do not see anything in zozbot234's comment that implies that Rust should strive for feature parity with C++. Some features, however, such as being able to use integer values as generic parameters, are arguably pretty useful.

Indeed. I think that's referred to as "const generics" in rust venacular