Yes. I don't think knowing about category theory makes you more proficient in using or designing functional languages either. Lambda calculus has much more obvious utility. Even things similar to monads can be described more simply without abstract nonsense: state is just another variable that you are passing along in your functions. The best books on Haskell do not dwell on category theory.
There's actually a bit of harm too: the abstract nonsense seems to make it harder to reason about execution speed and makes it very easy to write very slow code. I know a lot of people have a hard time being able to predict the speed with which, say, Haskell code will run.
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