> Your second line is a silly slogan which presumably means constraints make the job of picking one choice from a set easier due to less thought needed

That is absolutely not what it means, and it is not a silly slogan — it is a basic law of reality.

As an example, if your build system is monadic (build nodes can add new nodes dynamically) then the number of nodes in it is not known upfront. If the build system is not monadic, the number of nodes is determined at the start of the build process.

As another example, the constraints that Rust sets around & and &mut mean that the compiler can do really aggressive noalias optimizations that no one would even dream about doing in C or C++.

See https://m.youtube.com/watch?v=GqmsQeSzMdw for more examples.

> It is applicable to inexperienced developers but certainly not to experienced ones who need all the flexibility that a language can give.

I'm quite an experienced developer, and I've tended to use more constrained languages over time. I love the fact that Rust constrains me by not having uncoordinated shared mutable state.

> This discussion reminded me of "The Blub Paradox" by Paul Graham (https://paulgraham.com/avg.html) which i think most Rust evangelicals suffer from

At Oxide we use Rust and would never have been able to achieve this level of rigor in C++. Hell, try writing anything like my tool https://nexte.st/ in C++ (be sure to get the signal handling exactly right). Rust tooling is at a completely different quality level from earlier-generation languages.