Rust is funny because in one sense it's hard and clunky. However, it's only ever precisely as hard and clunky as it needs to be . Everywhere something can be made more concise, or readable, or convenient, without sacrificing any control, it has been. Anytime something is hard or inconvenient, it's because the underlying domain really is exactly that hard or inconvenient.
Contrast this with other languages, which are often clunky when they don't need to be and/or "easy" when they shouldn't be.
Meta-Comment: I started this topic as someone completely uninvolved in the rust project. It's very reassuring seeing the nature of the response. Even knowing how fantastic the Rust community is, I was still prepared to be met with at least a small element of condescension given the nature of this issue. I haven't felt any sense of it. It's amazing. Anyone that has impact on the community culture deserves credit: This sort of experience doesn't come from nowhere. It comes from a long history of many people nudging things in the right direction.
In many cases, it is possible to completely rearchitect the underlying code while leaving the public API as-is, and without introducing new bugs. I've literally never had such a liberating experience with refactoring until Rust.
mate it's like when you and the lads are on discord givin em classic bants but you wanna bang out some code and you're thinkin gems or eggs but your mate Yehuda who's a LEDGE AND A HALF says nah mate let's grab some crates and get our borrows checked and you're like SORTED
The reason why I think it makes sense to prioritize perf over everything except safety is that, if Rust is not the fastest high-level programming language, important systems will be implemented in a faster, unsafe language.
What's special about UB is that it attacks your ability to find bugs, like a disease that attacks the immune system. Undefined behavior can have arbitrary, non-local and even non-causal effects that undermine the deterministic nature of programs. That's intolerable, and that's why it's so important that safe Rust rules out undefined behavior even if there are still classes of bugs that it doesn't eliminate.