But we don't. He promises things like "repeal and replace Obamacare." That's fine, except that the important question is replace it with what? If it's a substantially similar bill that still includes expensive subsidies to private health insurance companies with poverty-trap-inducing means testing, that is not going to help people.

The people who heard "repeal and replace" are presumably expecting some kind of meaningful yet unspecified improvement in their situation. In practice that means somehow causing there to be more money in the pockets of patients/working-class-taxpayers and less for medicine-adjacent companies. The current politics doesn't allow that because those corporations have too many lobbyists. You can imagine people holding out hope for some strongman to come in and lay down the law -- certainly that's what the left wanted Obama to do with single payer.

A free market alternative might be putting a stop to the games medical companies play to evergreen patents and generally thwart competition through regulatory capture. But Congressional Republicans may be too corrupt to let anything like that go through, and it would be all too easy to interpret "repeal and replace" as just cutting back the insurance subsidies (i.e. means testing them even more) so they can use the money to give investment bankers a tax cut.

Suppose Trump bans all Muslim countries from entering US and somehow (dubious) it does not affect American businesses negatively while improving local hiring. What if that is not enough? (it likely isn't)

Whom will the electorate choose next? A full on warmonger perhaps?