The most destructive consequence of the Electoral College is its damage to the legitimacy of the Presidency.
(A reminder: ‘legitimacy’ is quite different from ‘legality’. The latter is achieved by following the electoral laws in determining who wins office. The former comes from the perception that the electoral process was fair. Thus, Mr. Trump, Mr. Putin, and Mr. Maduro are all legally in their positions. However, none of them can be said to be fully legitimate. By contrast, Ms. May, Ms, Merkel, and Mr. Macron are all completely legitimate, even if they suffer from low approval ratings.)
The Electoral College rejects the vote of the majority of Americans and favors a vote of the minority of Americans. This flies in the face of the most fundamental principle of democracy.
The authors of the Constitution made two blunders: the acceptance of slavery, and the Electoral College. The first blunder required a Civil War to correct. I cannot imagine any process other than a civil war that could correct the second blunder.