While there is a major emphasis on research and theory when it comes to Haskell, it's use of monads handling impure effects is what enables the language to be used as a legit programming language to develop things like web apps.
Haskell's emphasis on purity makes it seem like it can never get anything done (and it wouldn't), but it's impure aspect (monads) allow it to parse files, talk to databases, interact with the user, etc. But it still remains pure because the side effects happen inside these monads, which is just a type class at the end of the day.
I don't work professionally as a programmer (web developer) yet, had a temporary job working with Swift though. I'm just a pure self-learner building a portfolio right now and adding new things that interest me. I'm learning Haskell to build my third app. When I was working through the other apps I'd learn about something cool like JSON Web Tokens or Web Audio API and wanted to add it to what I was working on so I would do that. Deep Learning/Machine Learning came up from an idea I had about letting the computer analyze sports.
I did like Elixir/Phoenix and absolutely do see it as the next big thing. The fact that you could punch in 3 lines into the CLI and out comes a full on MVC is spectacular, add a few more lines to your code and you have web sockets that could serve something like 2 million concurrent users off of one laptop? It's insane.
I think though the "magic" of it and how it was presented was what discouraged me from learning it. I tried it out because I wanted to get into functional programming, but the way I dove in probably wasn't the best. I'm the type who likes to learn things block-by-block and under the hood from the ground up. The way the books explained Elixir (mainly Phoenix) was punching in those commands into the CLI to get a web app going and trying to learn what was happening. I just don't learn well that way. In the end I felt overwhelmed because I had to learn Ecto and Plug on top of the language itself, and because there were keywords everywhere and I couldn't tell what framework they belonged to was really confusing to me. I already experienced Javascript fatigue not too long ago and really didn't want a language that relied on outside frameworks out the box. Nothing wrong with the language itself, just wasn't the right time and explanation for me.
Maybe I'll run into it down the road though, because I do understand why many people love it. I definitely see it blowing up, and fast. If there's anything to challenge Node down the road, it'll be Elixir/Phoenix.