Fit for the job counts the most.
In 1980 I voted for Ronal Reagan. I thought Jimmy Carter a good person but too much of a loner or a micromanager to connect well with Congress or fully utilize the wisdom of his cabinet. I did not like all that Reagan did, but he knew how to get things done, and in balance got some good things done and along the way fully utilized his cabinet and connected to congress, at least in his first term. Hillary Clinton is not as likable or trustworthy as people want her to be, but she IS experienced in foreign affairs, how congress works and does take advice from others. Donald Trump is also hardly likable or clearly not trustworthy, but he is oblivious to foreign affairs, how congress works and does not take advice from others. On top of that he is thin skinned and impulsive, hardly what i want in someone who has the nuclear codes.
Third party candidates create risks of unintended and bad consequences
In 2000 many people voted for Ralph Nader as a statement of their desire to shake things up in Washington. As a result we got George W. Bush, who was not prepared to be president instead of Al Gore. Bush did not lead as much as he was led by others and by his own adolescent impulses (e.g. to be the "decider"). As a result, in his presidency we also got the biggest financial crisis since the great depression, with untold hardships for millions and the biggest foreign policy disaster in our history, with too many lives lost or injured by Americans and Iraqis and a chaos widening in Afghanistan, Syria, Yemen. President Gore would not have been without his challenges, but they would not have been at this scale. He had been a Vice President and a Senator. George W. Bush and Ralph Nader were not. Making statements about my beliefs, like in the Green or Libertarian parties today, should come second to being a responsible citizen; not allowing the wrong person to get into the oval office.
The President does not act alone
Congress counts. The charge has been that Hilary Clinton would bring about more of the same. President Obama did not get much done. We need change and Donald Trump would change things. But, and this is a big But, any president can only do so much. Congress for the last eight years has been devoted more to getting rid of the President than to governing the whole country. Mitch McConnell, the Republican leader of the Senate, declared that his top priority was "making Obama a one term president". What happened to his role in seeking better legislation through compromise? There have been areas where the majority of Americans have wanted compromise and did not get it: on infrastructure spending, sensible gun laws, to name two big things that would create lots of jobs and a lot more safety in our streets. But, Citizens United, gerrymandered districts and voter suppression laws have made sure that moneyed interests get their chosen people into congress and once there, those people find it easy to stay. All they have to do is pay back the people who bought them. They don't give a damn about governing, they just want to stay in office.