Haskell doesn't really have that many operators built-in (that is, in the standard Prelude). Haskell is completely open to user-defined operators (whose names can either be alphanumeric or symbolic), which, combined with the fact that symbolic operators often are attempt to approximate symbols from the application domain in ASCII while avoiding duplication of symbols used in the prelude even if those in the application domain are the same as those used in the prelude often results in less-than-intuitive choices.

Whether this is more or less readable than alternatives, though, is pretty subjective -- operators are generally used to reduce visual complexity in a way which is (given the constraints discussed above) as familiar as practical given the notation used in the domain, so even with the problems introduced by those constraints I think it often results in code that is at least as readable, and often more, than the cumbersome structures that are the alternative in languages that don't support user-defined operators.

I would suggest that is obviously false. Most languages have operators. Is 4+5 really less readable than plus(4,5)? Haskell does not have very many operators. The fact that people see 3 operators they are not familiar with and decide "this is unreadable because of so many operators" speaks rather poorly of people's desire to learn.