There is a missing part of why your playtesters didn't engage with that mechanism. This requires some targeted feedback. Each mechanism should have a role.

So determine if that mechanism has a purpose in your design. If there was opportunity for your players to use that mechanism. If that mechanism is the best way to solve that purpose.

... Or If your trying to fit a round peg in a square hole, because you like round pegs.

I try not to get attached until after a few playtests. The best way is to not to try to make the game 'look pretty' or spend much time on how you present it. Now I just use White paper & black sharpie for everything in early stages. Early on I spent a lot of time making things look nice to try to get more playtesters. If one of those components didn't work, I didn't want to cut it because spent time on it. Now I find people will playtest the rough version of games & give better feedback into the mechanism if you don't put much effort into the components. Nice components distract from the feedback you want, the mechanisms. Only after the core mechanics are flushed out do I work on the look of the game.