Many commentators--including Marc Thiessen--have noted a major policy consequence of President Obama choosing to push much of his agenda through executive action: because all of these policies depend upon the whim of the president, Donald Trump could easily remove most of Barack Obama's actions with the stroke of a pen. This renders the president's policies, ranging from the Paris climate accords to actions on immigration, about as permanent as a block of ice left outside-- seemingly solid during one political season but melting away during the next. Conservatives might rejoice at the impermanence of President Obama's legacy on many issues, and some on the left might lament this same impermanence. The president chose to push constitutional norms to their breaking point, and now the Left must reap the whirlwind.
On a deeper, structural level, however, there's something troubling about this highly mercurial policy situation. The more the federal government concentrates policy power in the hands of the president, the more unstable government policy becomes. Elections are in part about forcing change into the political system, but wild swings in government policy can also threaten the overall stability of the nation.
The executive does have considerable power, especially on foreign policy, but the legislative process sets limits on how much one president can diverge from the policies of his or her predecessor. When a bill is passed through Congress, the system of checks and balances gives the resulting law some permanence. Changes can be made, of course, but those changes have to go through a multi-part process in order to be realized (winning majorities in both houses of Congress and then, barring a veto-proof majority, the president's signature). Laws are rigorously passed, and their modifications have to undergo a similarly rigorous process. That's not the case with policies adopted according to executive whim. Governing by executive supremacy means calling for the nation potentially to careen wildly from one policy extreme to the next every four or eight years.
In establishing the Constitution, the Founders realized the importance of some level of stability for the overall architecture of the nation. The project of executive supremacy in part threatens constitutional norms by allowing the president to dictate policy, but it also threatens that broader project of stability. Hopefully, folks on the right and left will learn from Barack Obama's unfortunate excursion into executive supremacy.