There are quite a few very interesting and solid languages out there. One example for something that's not nearly well enough utilised or used widely is OCaml -- although in its case the lack of true multicore CPU support definitely cripples interest. But the language has an amazing type system that catches a _TON_ of errors (maybe even more than Rust's compiler, not entirely sure). And its compiler is just lightning-fast, fastest I've ever seen in fact. And it is multi-paradigm language (OOP and functional, and a lot of interesting typing constructs on top, half of which I don't even understand). Etc.

Not advocating for OCaml by the way (I work with Elixir and am looking to get better at Rust lately). It's just an example demonstrating that, again, there are a good amount of very solid languages and runtimes out there but we the programmers are so busy either (a) belonging to tribes or (b) being so damn busy we can't look beyond the tech we do our daily job with -- and then a lot of excellent tech gets left in the dust. :(

Mercury might be one of these tech pieces. And it's definitely not the only one.