When I first started out with Elixir, it was more the overall architecture that first sold it to me. It is remarkably robust, my impression is that you can more or less yank RAM modules out of the server while it is running, and the last thing which will crash is Elixir. And it is absolutely top in class when it comes to parallel processing and scaleability. Not only how it does it internally, but also how it abstracts this in a way that just makes sense when you are working with it.

When it comes to web development specifically, what really got me hooked, was LiveView from the Phoenix framework. It keeps a persistant WebSocket connection to the client which it uses to push DOM updates directly. Instead of the usual request/response cycle on the client side, the server holds the state and just pushes the diff to the browser. It just made so much sense.