Rust 1.0 was released in 2015, and before that you'd have breaking changes every month that effectively made it unusable for anything but toy projects. So it's not even 5 years old really.
Besides a big target for Rust is the C and C++ world. On Hacker News in my experience you have a majority of commenters coming from the web world where no news in one year effectively means that the project is dead.
For us in the low level world "stable for 4 years" means "maybe we can start considering using it in production" and the lack of big buzz every other month is more a pro than a con. I'll take boring and reliable over shiny and breaks-every-other-year.
I've just started adding a new feature on a C project started in 2009. If I used Rust I'd want to know that my dev environment will still be usable in 2019. I think the commitment to stability will pay off eventually.