For web development I would suggest to take a look into Elixir. Elixir is extemely good for real time apps through websockets, apps with a need of high concurrency and / or apps where you need to process hundreds of thousands of states of differents users in parallel thanks to the actor model that comes with Erlang virtual machine. To solve these kind of problems in another stack could be really hard and painful (including your current stack).
It's true that Elixir is a niche stack ( It deserves way more popularity in my opinion), so, if your concern is to learn something that would keep you inside the trend and market, instead of Rust or Elixir I would suggest Go. Go it's another outstanding language, will a lot of virtues, small and easy to learn, with it for example, you could compile the same application to different operating systems just with a special compiler command (And the compiler is blazing fast). You can also start with a lot of good libraries that helps you to keep your code clean and under control and of course, it's performance is very good too.
Hope my suggestions could be helpful.
Best regards, and happy coding!