Reagan may have been a registered democrat, but his ideology was always staunchly conservative, which is why he eventually switched to the Republican party. Trump not only was a life-long democrat, but he also supported the entire liberal agenda for the last 30 years, including sensible gun control, anti-capitalist movements, pro-abortion, pro-gay marriage, and even pro-amnesty. Remember, Trump even criticized Romney for being too harsh on illegals despite Romney also being pro-amnesty. Trump only changed to a more conservative tone on immigration during the last 2 years, but the rest of his policies are still extremely liberal. That is the big difference. Trump was and is a liberal so Trump is definitely no Reagan.
It boggles the mind that conservatives think it would be anything but disastrous to elect a lifelong liberal.