Actual interface designers communicate functionality and state through an interface. If your designer is designing interfaces that look good but are less functional for the intended user base, you’ve hired a graphic designer that claims to be an interface designer. It’s not a problem you can generalize to design or designers any more than someone can generalize that web developers suck because the ones they hire to build a serious web app are really Wordpress plugin hacks that don’t even realize they aren’t web developers.