For thousands of years, horses were productively employed in the transportation industry. When the automobile was invented, they were unable to find gainful employment and their wages fell below subsistence levels.

This hasn't happened to humans yet because technology has not replaced all possible jobs humans can do. That doesn't mean it can't happen, it just means it hasn't happened yet.

Because economics is not a science. Don't believe me? When was the last time someone published the results of an economic experiment and another economist was able to reproduce it?

Economics is a social science, not an empirical one. This is why people who perform those experiments fail; they fail to see the difference between the success of empirical approaches to the natural sciences, and the failure of it to the social sciences. Social sciences are advanced through dialect and reason. But this still doesn't mean that we shouldn't approach these studies with humility and be careful about the things we postulate.

I'm long past the point where someone was ignorant of something and it upset me. I've come to realize that I, myself, am ignorant of many things. I no longer see it as a crime. What I see as a crime is people acting and opining on things they haven't given plenty of thought to. We all need to be careful to not spout-out answers and opinions that we always carry at the tip of our tongue. It's worth it to be humble and skeptical all at once, but it's tough.

I think you just destroyed astronomy, cosmology, and geology too. Some sciences are more observational than experimental.