ingenious but pointless trick; artifice for its own sake
A yojijukugo describing a clever or elaborate technique that ultimately serves no practical purpose; often used critically.
His proposal was nothing more than an ingenious but pointless trick, and it was of no practical use.
From Classical Chinese 奇技淫巧, occurring in the 『書経』 for ingenious but excessive contrivances made to please or beguile.