For many types of projects and approaches, avoiding UB is necessary but not at all sufficient. It's perfectly possible to have critical bugs that can cause loss of health or life or loss of millions of dollars, without any undefined behavior being involved.
Funnily enough, Rust's pattern matching, an innovation among systems languages without GCs (a small space inhabited by languages like C, C++ and Ada), may matter more regarding correctness and reliability than its famous borrow checker.
Possibly, I am not sure, though Delphi, a successor language, doesn't seem to advertise itself as having pattern matching.
Maybe it is too primitive to be considered proper pattern matching, as pattern matching is known these days. Pattern matching has actually evolved quite a bit over the decades.
Funnily enough, Rust's pattern matching, an innovation among systems languages without GCs (a small space inhabited by languages like C, C++ and Ada), may matter more regarding correctness and reliability than its famous borrow checker.