Never claimed it would be. But I've been bitten enough professionally with services written in Python and Ruby eventually costing the company a ton of time, effort, money, and operational risk to replace because those language runtimes just cost too much to operate at scale.
I would probably reach for Java (or ideally Scala) for that sort of thing these days, but would love it if something like Rust could compete in that space. Maybe it can't, but I wish it could.
I think one place where Rust could be great for these sorts of things is low-horsepower devices like routers and managed switches where you want to have a rich web interface but can't afford the overhead of an interpreted language. Being able to ship a device with a slower CPU or less RAM/storage because its web UI requires fewer resources would be an advantage in a market that's already very price-competitive.
Just to disclose my biases: I'm of the opinion that you shouldn't ever be writing anything in a dynamically-typed language if you expect it to turn into a large program. Your initial development will indeed be rapid, but later on you'll be spending more time writing tests than improving your software... or you won't be writing tests and will be too afraid to make large changes without breaking something.
