While all candidates spout platitudes, the big difference with most others is that they have a record to stand on. In fact, if they were to say something radically different than what they've done we would doubt them, such as Rubio's newly found anti-immigration position.
With Trump is different. We have no clue what he stands on, and "I'm going to bully the world to do what I want" is a play yard tantrum, not realistic policy, in spite of what you write above.
Lastly, the problem with immigration can be solved in an instant if you really want to: put strong penalties on employers for hiring illegal immigrants. It was tried for a year during the Reagan administration and it was highly effective. This is how all other countries on earth do it. The reason it is not done in the USA is because it businesses need illegal workers to cover the bottom end of the spectrum. So you can do this bluster about a wall, which impresses simpletons, or you can propose an actual solution and then you have the entire business lobby against you.