I just think the current emphasis on inequality of outcomes and headline numbers like income share leads us down the wrong path. Those are effects, not causes or even the effects that directly drive discontent; yet by emphasizing those aspects we spend an inordinate amount of time on measures that attempt to address those symptoms specifically rather than the causes. But also...

1) Income share is complicated: https://equitablegrowth.org/labors-share-lost/ There are structural issues, like automation and immigration, underlying those trends. Immigration isn't, per se, irrelevant, especially when you consider dynamics like volatility and displacement. (But, again, it's complicated.)

2) Throughout history vilifying the rich has not worked out well for the poor and working classes, neither in absolute nor relative terms. Where sustainable improvements have been seen, they're the result of a flattening of the social hierarchy (not necessarily in monetary terms!), but in a way that shifts norms to the type of long-term, group management that you see in the upper middle classes, not the winner-take-all, rat race rules of the poor (at least, that they see as governing inter-class conflict, not necessarily among themselves). The cookie metaphor, both in the model it presents and the devious motivations it insinuates, is rat race rules, and rat race rules favor the rich much more than cooperative, inclusive norms. What you want is for the wealthier to identify with the poorer, but that can only happen (if at all) to the extent the poorer identify with the wealthier. If some wealthy person perceives themselves as having been wholly self-made, despite what's obvious to everybody below him, good! That implies he at least values agency and work ethic, norms that in the United States can be and are shared with people below him on the ladder, and therefore a way to sell political concessions as being in his self-interest (psychologically).

3) Wealth (as opposed to income) doesn't work as implied in the cookie metaphor. Elon Musk is a trillionaire, but there's no bank vault with a trillion in gold bullion that he can go to at will. At any point in time--hour by hour, even--his nominal wealth is primarily a function of the future expectations of others, including expectations of social contentment and economic growth. You can't take half of Musk's cookies and redistribute to everyone; it's entirely non-sensical to think that way. Our intuition breaks down at scale; certainly from a process perspective (as opposed to a static context). Just like running a $30 trillion national economy isn't the same as running a small business (for one thing, nobody runs it), the cookie metaphor leads to horribly misguided ideas about the nature of our problems and the viability of remedies.

Yes, inequality of outcomes matters (at least at the margins), it just doesn't provide much if any insight into causes and solutions. Imbibing in zero sum cookie narratives is counterproductive. Like other forms of social injustice, e.g. racism, it's paradoxical--how can you fix something without identifying the effects with an intention to address them; yet, such a fixation has a tendency to solidify (reify?) the divisions undergirding them. If you look at critical theory, especially critical race theory, you can see an admission of this paradox at the core of the literature. People like Frantz Fanon and Derrick Bell came to the conclusion that it's impossible to completely overcome racism--systemic and otherwise. Their perspective is understandable given the seeming intractability of these sorts of problem, I just don't share the fundamental pessimism at the heart of how these issues are framed by contemporary social justice thinking. And it's that framing that I saw in the cookie metaphor. I don't have the right answers, but history has shown us the wrong answers.