This is a tricky one. If the abstractions were not leaky, you would not be able to interoperate with JavaScript libraries and you'd have to reimplement everything that powers the modern JS ecosystem. On the other hand, if the abstractions were too leaky, you'd lose all benefits of a nice language like F#.

I think Fable strikes the right balance. There are some leaky aspects of how it compiles to JS, but this means that you can quite well use it with existing JS libraries and for things like parsing JSON (you can just cast JSON object to F# records and it'll work).

So, you need to think about something about the JS part when you want to do JavaScript-y things, but you still get plenty of nice help from the F# compiler when writing the logic that the functional-first style makes so much easier.

In my experience with Fable, this pragmatic approach is what makes it great.