It seems like the current way of doing things leaves the opposition rudderless through most of a presidential term, followed by a bitter fight where their own side rip each other apart followed by only a few months to try and establish oneself as leader in waiting.
Could the democrats do their primaries now? It feels like that would 1. Distract from Trump so he doesn't get run of the news 2. Mean that all the "candidate X is a bad democrat" stories could be long forgotten by the next election. 3. Give a pedestal to the actual presidential candidate as the go to person for the media to get reactions from 4. If they turn out to be genuinely terrible there's a lot of time to find out and potentially replace them.