[madhouse]

Either you don't mention it, or you mention you did grunt work, what you've been told, even if you knew you could've done better.

Something like: "Despite my numerous attempts to convince the powers that be to implement $solution using $awesome_stuff, the policy remained the same: stick with $ancient_pile_of_dog_poo. But a job needs to be done, and so it was."

This has the advantage of suggesting that you will do what you're told - not neccessarily without trying to have your say first, but eventually, the job gets done.