I'm currently learning and loving haskell. I, however, find it unlikely that this language will ever become mainstream.

Throwing a beginner head first into recursion and restricting all their programs to be a singular composite of expressions is the, unfortunately, best way to turn away a beginner.

But damn, it'd be an awesome future if I'm wrong.

The alien-ness is what makes it difficult, not the actual design. Less design surface area makes it considerably easier to learn in that respect. That doesn't mean Haskell is easy to learn in general, for now. There's a huge difference in jumping from Ruby->Python->JS vs. learning how to program in terms of a foundation built on lambda calculus.

"singular composite of expressions" - this doesn't mean a lot, and doesn't really fit, I think. You can hand-wave do syntax and pretend you're writing imperative code in IO. A lot of people do that when first starting out so they can get the hang of things. SPJ (OG Haskell honcho & compiler hacker) likes to say that Haskell is the nicest imperative programming language to use. I'd tend to agree :)

Takes practice. You need exercises.

If you haven't already seen it, I'd recommend taking a look at the guide I've maintained on how to learn Haskell: https://github.com/bitemyapp/learnhaskell