This kind of comments make me really sad. Most ReasonML developers are actually "JavaScript developers".

ReasonML was specifically designed for JavaScript developers. Being JavaScript-friendly is in it's DNA really. I even see ReasonML a language that was specifically designed to work with React.

I can understand why you would feel this way though. I think the main problem is that ReasonML introduces new concepts that simply do not exist in JavaScript. Learning those concepts is hard. But if it wasn't hard, would you be learning anything or just writing JavaScript in a slightly different way?

Are there any specific examples of things that look too "distant" from JavaScript?

I'll finish this by saying that ReasonML will make you a better JavaScript developer. As will probably learning any other language that challenges the way you think.