I think their point was tax cuts/deregulation happened to be his biggest policy successes, not that they necessarily are the only things that matter.
They want to ascribe Trumps success to the Paul Ryan led Congress. Its very clear what the angle that WSJ has here...
And if the past is any sense of prologue the traditional republicans will fight hard for nothing else other than tax cuts and deregulation while the country degrades into a ****hole.