No Nixon Presidency, no Bill Rehnquist, no Roger Stone, no Ed Meese, no Dick Cheney, no Nino Scalia, no John Roberts researching how to overturn the voting rights act. Gods, the list of bad people who got their start with that man in power....
Not that Republicans would have been aced out of power forever, of course. Or that RFKSr would have been immune from fumbles and free from fault. But even Reagan was just a mile post on the racetrack set by Nixon. (Paging @rufus-hickok.bsky.social )
Yeah, it's entirely possible that my memory is limited to my own lifetime, where Trump feels like the real life version of the character Reagan played. I've also heard the case that everything in the Powell Memorandum (1971) came to pass, although that was mostly about destroying higher ed.