ReasonML is just a PP (preprocessor) for OCaml. You can generate normal OCaml programs with it, or plug in other OCaml backends, like say JSOO or bucklescript (or whatever its called now) to generate javascript for example. ReasonML comes with a very node-centric array of ecosystem tools to fit in to that all though, quite easy to pick up.
That community has a lot of churn though. In general there’s a small set of dedicated people who stick around, but a few select some of them are rather hostile to new users, which tends to drive them away.
As for the language, it has a lot of design issues, many of which have repeatedly caused miscompilations over time, and that’s even before getting to the elm architecture style of doing things (which is just a standard centralized event processor), which is overall fine, but rather difficult to work with, especially when combining with other things for a variety of reasons. I tried to use it in earnest for over a year, but a combination of language misdesigns and the hostile community were, not pleasant… >.>
Even things like the OP article just outright lying (there is no TCO in elm) has been a common pattern over time.