I quit using Rust in 2013 due to the learning curve. There's just no way I could have asked anyone else to use it.
Keep in mind that Rust 1.0 was released in early 2015, and it's not like they were making major changes right up to that release date. I haven't followed it recently, but I doubt it was meaningfully different from the 1.0 release in terms of learning curve.
Rust was still changing quite a lot in 2013. It sounds like you used it back when it had a garbage collector, baked-in green threads, and "~" and "@" sigils everywhere. Rust 1.0 may as well be a completely different language.
Here's a blog post from the same year that proposed removing the garbage collector.
Keep in mind that Rust 1.0 was released in early 2015, and it's not like they were making major changes right up to that release date. I haven't followed it recently, but I doubt it was meaningfully different from the 1.0 release in terms of learning curve.