I think the issue in 2016 was too many people wanted the job. You can agree/disagree whether the primary field included 'outstanding' people, but the sheer number of candidates allowed the loud mouth to stand out.
Some sort of approval voting or instant-runoff would probably provide better outcomes.
I think it's obvious if the US worked this way, the Republican party wouldn't have selected Trump. Perhaps you end up just electing the same old boring white guy time and time again.
So, we have primaries for each party. Some states are open (anybody can vote, but only for one party's candidates) while other states are closed (only party members can vote). Then, after the primary winners are selected, there is a general election where to select among each party's winners.
Most of these elections are plurality, although some states require majority (with runoff between 2 top candidates).
Basically, this leads to extreme candidates winning the primaries, then trying to pivot to center for the general election. It also means that if a primary has many options, as the GOP 2016 primary did, you get results like Trump - all the reasonable candidates cancelled each other out.
Pivoting to approval voting would be relatively easy - the ballots don't change much (just allow 1+ choice per race). We could maintain party/state primaries and a national general, but move them all to approval. That would avoid 3rd party spoilers and hopefully prevent the fringe of either party becoming the nominee/winner.
This ignore the added complexity of the Electoral College. That's an anachronism for another post.
You can think of election cycles as a series of games of rock paper scissors. Not uncommon for the winner of the primary to be a guy that can't win in general. Scissors beats paper in the primary. Goes up against rock in the general and loses.
The issue was that a relatively large number of them had financial support and sizeable backing within the Republican party until late in the campaign. That's less likely to happen if there's one outstanding candidate. For example, it didn't happen in 2020, not because nobody else wanted to be President, but because the GOP overwhelmingly agreed that Trump was their best bet.
The problem is, Trump = big ratings for the media on both sides. MSNBC is as much to blame as Fox. It's also imho partially the DNC's fault (the left has less choices), and they picked a flawed candidate who would've never won against any of the RNC choices.
She had a criminal on-going investigation, which true or not should've been like, woah, let's maybe put someone else in, who might not be indicted.
The entire system is fubarred and there's plenty of blame to go around, I don't know where we go from here, and I highly doubt a Biden administration is going to bring much joy either to a lot of American's who are suffering.
I do hope we make it harder for something like this to happen again (for fascists to take such strong control in America).