The problem isn't the lack of critical thinking processes on the part of (most) candidates. It is the lack of critical thinking processes in voters. When republicans have an ever growing checklist of requirements to be considered a "real" republican (and now need a blessing by king Trump) they need to put any critical thinking skills they have on hold. Which is why the only congressmen willing to stand up to Trump are the ones on their way out the door.
Democrats look to be following the same playbook, as recently there have been suggestions from some democratic donors that potential 2020 democratic candidate Beto O'Rourke isn't "progressive enough" and actually said electing him would be like electing Obama again. Bernie or bust I guess, nevermind his age. Just like Bush and Reagan couldn't win nomination in today's republican party, perhaps before long Clinton (Bill) and Obama couldn't win nomination in today's democratic party.