The reason people are terrified of an authoritarian regime isn’t because a dictator Republican is going to force lower taxes on people. It’s because of the state and private violence. I may have hated Reagan and W because of their policies, but neither of them would have tried to overthrow the government of the US and replace it with a dictatorship. If either of them lost their election, they would have conceded. Neither of them promised while running for office that they would enact a dictatorship.
The problem with your question is that you’re assuming that what we have an issue with are republican policies. It’s true, we do. That’s not the biggest problem with Trump, though, and the linked article makes that quite clear.
To be honest, I wish Obama had been more successful in passing a national healthcare program. I hated that he had campaigned for Lieberman (because the default position is to support the incumbent) rather than his from-the-left challenger in the primaries, and that L went on to tank the public option. But I wish that Obama had used every ounce of political power to ram it through, or had thrown L to the dogs and went all in on getting a more liberal senate. I don’t wish Obama had dictatorial power.
I don’t even particularly favor having an executive branch that’s separate from the legislature. I think that parliamentary democracy is a better approach (although it has its issues too).