Fun story. I showed up at my current company, and some frontend dev had convinced everyone that everything should be written in Elm. Their phone client, the frontend website, everything. Then, their lead dev left and so did the frontend dev. Lucky for me, only one part of one page actually made it to production. But this was around 9 months of multiple developers' time just flushed down the toilet. None of it was usable, none of it was worth learning Elm to finish.