Often the bad designs come from the designers themselves. Just as software developers often fall prey to "NIH", many designers feel the established design systems like Material are insufficient for some reason. That is OK, if you know the rules you can break them, but often they don't know the rules either (grid system, typography, color for accessibility) and want to make "their own mark" with some new creation that…
I don't have any strategies, but I've had designers also want to add unnecessary steps to a gui-driven process. One designer kept arguing about the cognitive load of having a user simply insert their credit card into the reader to signal intent to pay. They wanted a flow where the user would touch the UI to indicate whether they wanted to tap or insert or scan a coupon. There was no reason to do it that way. I don't want to get into the specifics but it's a flow everyone uses every day without thinking and we were adding a new input device. It's not like we were inventing an entirely new system. The designer just wanted to make the work more than it was.