I think intuitive understanding gained by practice is enough for every programmer, not just me. Learning by programming is easier than reading research papers and digging the theory. What more, it was a prerequisite for me: I could not understand papers on type systems or category theory before I saw Haskell code. I heard similar opinions often - Haskellers learn Haskell first, can code comfortably, and only then are able to read about the theory. Theory seems hard, dull and useless at first. Even now, I feel a lot of it is cruft.

The semi-official motto of Haskell is "Avoid success at any cost", not world domination. It is enough as a tool for hackers, not for everyone. Haskell expands extremely slowly, yet steadily.