Any hope for US capitalism redeeming itself in the next 4 years went out the window with Bernie Sanders's campaign.
Approval voting. You want approval voting. Range voting is actually better but approval voting is almost as good and is a lot simpler for people to understand, and both are better than IRV.
Moreover, the problem you're trying to solve is Arrow's Impossibility Theorem, which is provably impossible to do. You could have a third of voters prefer each candidate but majorities prefer Nader to Gore, Gore to Bush and Bush to Nader.
Only the Gore voters have to do the same thing, and then Nader wins if he has more support. Because a small percentage of people will vote only for their preferred candidate and risk Bush, which will be proportional to the support that candidate has and thus give Nader the win if he actually has more support.
The thing you're really objecting to is why range voting is better than approval voting. With range voting the Nader supporters can give Nader 10, Gore 9 and Bush 0, the Gore voters swap Gore and Nader and then there is less brinkmanship necessary to get the right outcome. But that's the cost of using the one which is easier to explain. And range voting is more complicated than approval voting, but it's simpler than IRV, so you're really just making the argument for range voting over approval voting.
I feel like the trap you're falling into is to grade approval voting based on whether it does what IRV does.
The problem with IRV is that it tends to do crazy things. So for example, imagine everybody expects that in a runoff between Bush and Nader, Bush wins. But between Bush and Gore, Gore wins. So then people who would vote for Nader can't vote for him because it would give the election to Bush again. But even weirder, Bush voters can vote for Nader in order to give the election to Bush. So IRV doesn't solve the most important problem, because people will still be clamoring for third parties not to run and for people not to vote for them for fear that they'll harm the major party most similar to them.
Thing is, w.r.t the economy, what can actually be done? The only thing I know of that isn't pretty disruptive is as higher inflation target - and we cannot maintain GDP growth to hit the one we have.
Nobody is doing the right thing. That's why the Republican voters nominated The Joker and the Democrats almost nominated Sanders. People are for someone who will shake things up. But the fact is nobody knows what Trump will actually do, so your choices this year are between "clearly bad" and "wait, what?"
And how can you possibly say he is part of the DNC? Do you even follow US politics at all?
That's a little bit of a stretch.
Inequality is a problem mostly because:
A) The benefits of globalism go to the 1%, then to the middle class in terms of cheaper prices, but the working class lose jobs.
B) US has massive importation of low-skilled immigrants. They go right at the bottom. You don't need a 'messed up system' - if you just add poor people, you increase inequality.
C) Bernie is an old-time socialist - he has no new ideas, really. I've heard him talk, he wants to massive increase wealth distribution and do it by taxing 'the rich'. This never works out, really. 'Infrastructure' is a cover - really, it's a wealth transfer exercise. Europe and Canada tried that in the 1960's it didn't go s well.
The problem is really difficult, and it's exacerbated by the sheer size of the US, also there are no ethnic ties. Sweden is only the size of Los Angeles - and they are 'Swedes' an ethnic group with fraternal social order, a Monarchy, a State Church, common cultural identity. It's easier to 'redistribute' when the person getting the service is someone you know.
The best kind of 'redistribution' is 'jobs'. Surely, increasing the minimum wage a little bit might work, and possibly having unions where none exist (Wallmart?), but strengthening already existing unions - particularly in the auto-sector and government is not going to help anyone - they are part of the problem. Auto workers and gov. workers are massively overcompensated relative to their private sector peers. Gov unions are one of the reasons government is so massively inefficient. If Bernie could fix that, that'd be great - but he's a politician, he's never had a normal job and wouldn't have a clue how to do it.
I think moving towards empowering people, making sure they can participate in the global wealth creation is very important, but 1960's style socialism is not the answer.