> So I think "no gc but memory safe" is what got people to look at Rust, but it's 1990s ML (ADTs, pattern matching, etc.) that keeps them there.

Yeah; this is my experience. I've been working in C professionally lately after writing rust fulltime for a few years. I don't really miss the borrow checker. But I really miss ADTs (eg Result<>, Option, etc), generic containers (Vec<T>), tuples, match expressions and the tooling (Cargo).

You can work around a lot of these problems in C with grit and frustration, but rust just gives you good answers out of the box.