You assume if productivity goes up 2x, it's the employee that's twice as productive. From the business owner's standpoint, that's not the case. If a factory employs 1000 people and then completely automates everything and only employs 1 person to make sure nothing goes wrong, is that guy suddenly 1000x more productive? What about if it is a true "lights-out" factory that employs 0 people, now the (nonexistent) employees are infinitely productive? I'm really just playing the devil's advocate here and don't really think that way but the company owners sure do. From their point of view, they had to provide and tie up the capital and take the risk of buying the robots, why shouldn't they get all the rewards?
Not necessarily that the employee, as an individual is, but overall the per-worker productivity of the economy goes up.
The risk of buying robots is relatively small, and the company owner doesn't take 100% of it, its shared among all the stock holders, the insurance, the remaining employees, and (if its considered a critical industry) the government.
As to capital, well, that's the basic question: should having capital to invest entitle you to disproportionate rewards relative to your (individual) contribution to society?
In the USA, this is pretty much a lost cause... Sure, a lot of people talk about basic income but it will never happen.
This has been said before, in other contexts. Why would either employers ever agree to or government ever mandate limited daily work hours, weekends, workers compensation, unemployment insurance, vacations, medical benefits, overtime pay or minimum wage?
Both parties are owned by the rich and powerful and the voting system ensures that there can only be 2 viable parties. The only way to change that is through legislation but the very people who would need to pass such legislation to change the system are the ones who benefit from the status quo.
Change happens slow, and I agree with your assessment of the self-sustaining 2-party system today - although, we, collectively, certainly we
could change it, if we really wanted to, by just all voting for a 3rd party candidate. That too, has happened before. The two parties used to be Federalists and "Democratic-Republicans". Then there was the Whig party. The Republican party was once the 3rd. Change happens slow, but it does happen.
It's like congressional term limits or marijuana legalization, the majority of the country support those movements but their representatives ignore the will of the people for their own reasons.
28 states have legalized marijuana (either medical or recreational), and up to 8 more are expected to this year. That's over half, and a significant majority by population, as CA and the NE have the densest populations.
The thing about term limits is it actually anti-democratic - if the people think a senator or congress person is doing a bad job, all they have to do is not vote for them. The 2-party system doesn't even prevent that, that's what primaries are for. Every two years the people get two chances to replace a senator they don't like - or keep one they do like - and term limits takes that choice away from them. When term limits were an item on state ballots, the majority of states voted them down (8 for, 16 against), so even had the supreme court allowed it, the reality was most citizens didn't want to limit their own choice.