If happiness is relative and based on perception, could you make the argument that making everybody equally poor would be just as beneficial as contributing to everyone's success, rather everyone willing to work for it? If you continue to move the "goalposts of happiness" you could end up in a situation where there is the potential to do right by 98% of people, but you decide against it so that the 2% don't feel bad.
I suppose that is the logical reductio ad absurdum counter-argument. I'm no idealist, obviously some level of inequality is inevitable because humans are fundamentally different from each other in their abilities. I think it's really generational wealth and social mobility (two sides of the same coin) that are the important factors. Everybody knows that there will be "losers" in any game, whether it's a video game or the more serious economic game that we all play throughout our lives.
I think the disaffectedness of the not-well-off is due to a sense of helplessness that even if they had the ability and wherewithal to contribute to the world and better their own lives, that they wouldn't be able to do so due to factors that are out of their control, not out of some misplaced belief in equity-of-outcome
Note that I'm not railing against meritocracy. Rather, it's that the system currently equates a lot of "merit" with factors that very highly correlate with having a wealthy upbringing. Also, meritocracy taken to its own reductio-ad-absurdum of a small group of extremely capable people controlling all wealth is not in itself desirable - just because it's theoretically possible to achieve upward social mobility by being part of the top 0.01% of intelligence/capability/whatever doesn't mean it's "fair" that success is reserved for such a small group
