> I do not believe that the rich getting richer is the cause of the stagnation, though. If anything, automation and globalization have been the main reasons for stagnation among middle and lower income levels.
Who disproportionately benefitted financially from automation and globalization?
> From that perspective, I prefer policies that focus on wage growth for the lower and middle classes, even if that's a harder problem to solve.
You need to do both. No one was talking about this 20 years ago because most people were participating in the "good economy", even if some benefitted far more than others. Now people are being told the economy is good (by both major polities), but it doesn't match reality, which you noted is a major cause of angst.
Additionally, if your goal is to create more jobs and wage growth for low and middle income people, the best way to do that is to reduce economic concentration and create more opportunity for competition and small business. It will be less cost efficient, but the economy will be more resilient and the wealth would be more broadly distributed, even though some people could still achieve obscene wealth.