The Executive branch effectively only has the purpose of destroying, stopping, blocking, canceling, and annulling things. The president vetos bills; stops foreign invasions with military power; commutes federal prison sentences created by the judicial branch; stops legislation from applying by signing trade agreements or granting amnesties; etc. And every department within the Executive, like the FDA or the SEC, exists solely for the purpose of blocking people from doing things.

So the President is effectively just sitting there in front of a control panel consisting entirely of big red buttons. Sometimes, rarely, situationally, it helps to press one of them. Pressing one at random, though, would almost certainly do damage and serve no purpose.

Obama's status quo was done by just avoiding pressing the big red buttons. That's bad in one way. But it's an entirely different kind of bad to start pressing lots and lots of the big red buttons. That's what George W. was actually hated for—what he did, not what he didn't do.

Trump couldn't accomplish much good, certainly. But he would have full access to a panel of big red buttons. Do you trust Trump there?

Now I'm going to delve into specific politics more than I normally like to do, but I think there are important ideas to consider. Even if a president doesn't do what he/she promised to do, the attitude of a president does have an effect on the country. Judging from the attitude of Trump and the raucousness of some of his rallies, I don't think Trump's attitude and that of his more violent supporters should be spread across the country. That alone is enough reason to vote for someone other than Trump.

It's pretty sad, though, to have several elections in a row where more and more people are voting against a candidate rather than for a candidate. I can only think of one current candidate who I would vote for positively, rather than to just to avoid another candidate who is more negative.

Just because you get something worse than you wanted or expected doesn't mean that it doesn't matter.

Your idea seems to be more of an observation of recent presidents than a property of the presidency itself. I think there are two things that make it so. First, modern presidents are generally picked from a very narrow pool of candidates which the parties and the media help select and shape, thus making sure a relatively docile candidate is chosen. Second, most modern presidents are very politically oriented and beholden to the groups that donated to them during their campaigns.

I think that can be used to describe Hillary, but I think both Sanders and Trump are non-docile and not beholden to outside interests. Sanders, because his funds largely come as a mandate from individuals and he is very clear about who he works for. Trump, because he has nothing at all to lose by doing whatever he wants.

Would that be illegal? Would it be speech? It's not like the President would be telling you who to vote for (though it might be different if the US had referendums, because the President would be telling you what to vote for); the President is simply attempting to sway your opinion, and then telling you to inform someone else of your (hopefully swayed) opinion.

Consider, for example, a Sanders DOJ vs. a Trump DOJ? (I suspect a Trump FBI would be primarily interested in cataloging and spying on anyone critical of Trump or of Muslim faith, essentially use COINTELPRO as a starting point, but make it better and stronger and do good deals). What about a Sanders DEA? EPA? DHS? The executive can do nearly anything if they are bold enough. The executive can ignore the judicial branch ("He has made his ruling, now let him enforce it"), the legislative branch (subpoenas from congress? About illegal leaks of classified information for political purposes concerning Valerie Plame? Please direct the law enforcement officers with weapons in your branch to serve them. You don't have any?)

I believe Sanders would refrain from using executive power to make things worse, while I am certain all of the other candidates would not refrain. Hillary will not differ from Obama nor does she claim to. Trump's shtick is to be an American dictator, an executive strong man who advocates violence and abuse towards anyone who disagrees with him and acts as an outlet for racism and hate and anger. Imagine if he had an army of FBI, DHS, NSA agents at his beck and call.