Lots of financial companies, including some serious heavy-hitters like Bloomberg, use functional languages like Haskell and Ocaml. I suppose the blockchain folks are pretty enamoured with it too.
Plenty of big companies like Twitter use Scala, which is plenty functional.
Even on the front-end side: JavaScript was directly inspired by Scheme; TypeScript was hugely inspired by languages like Ocaml and Haskell; React and Redux's inspirations fall directly out of the functional programming community.
Rust, out of Mozilla, is also a descendent of the functional programming world; its compiler was originally written in Ocaml.
Just the other day there was a conversation on here about type-system enforced optionals. Almost every "modern" language has grown these in the past decade, often including monadic combinators to help minimize boilerplate. All of this comes from what ML and Haskell were doing as many as 30 years ago.
Speaking of monadic combinators: these are also frequently used in modern languages with async libraries to avoid what the JS community termed "callback hell".
TBH if you've developed software in the past ten years, it's unlikely you haven't been hugely affected by what the FP community has been doing, and it's not impossible that watching what they're doing now give you a glimpse of where mainstream programming will be a decade or more down the line.