> So... Type signature `Int -> Int -> Bool` can be used for a function that does any of the following things: manipulates strings, decodes JSON, or queries a database? How does that make it easier to deduce what a function does by "looking only at type signature"?

From this quote, it's easy to see you've not spent any time actually using Haskell (others have explained what is actually going on), so why do you dislike it? I cannot fathom having an opinion either way on a language I don't know.