Well to be fair, you can very easily argue that Gothitelle is broken with Shadow Tag whereas Wobbuffet is not, meaning that the qualities that Gothitelle possesses combined with Shadow Tag are what makes it broken, not Shadow Tag by itself. Specifically, Gothitelle's ability to attack, access to Trick (which allows it to revenge kill and stall break), and good coverage allowing it to pick and choose what it revenge kills are what allows it to use Shadow Tag in a way that makes it broken. Since Wobbuffet with Shadow Tag isn't broken, but Gothitelle with Shadow Tag arguably is, doesn't it stand to reason that we should ban Gothitelle and not Shadow Tag?