Good observations.
To make a slightly different argument, a modern day democrat who would take a traditional moderate democrat position could pull a lot of votes away from Trump. But it won’t happen because the DNC controls who the nominee will be through its money, messaging, and control over the media and they’ve lost touch with the electorate.
My democrat Rep is pretty moderate on local issues, very good at the retail politics, and understands her district. If she didn’t vote for the wrong crap and spew DNC talking points there would be little difference between her and the previous republican. It is the Uniparty after all. But the D side is run by crazed liberal progressives and the R side is now run by Trump. Notice how many turds have been excreted already: McCain, Flake, Corker, and most recently Amash. Yeah we got Romney but the ratio is favorable.
Mitt Romney isn’t all that terrible when it comes to business affairs; but his social politics are horrid. And America has a social problem right now which threatens to undermine everything else. It might have been a blessing in disguise to have gotten Obama rather than Mitt. Obama was more open about what he wanted.