I believe the transition to post-scarcity will be gradual, that it will happen faster in some sectors of society than others, and that this process may take multiple generations to complete. This has been the case with every other major economic shift, why would it not be the case with post-scarcity?
If this is how the transition to post-scarcity occurs, societies will eventually hit a point at which many people still need to work to produce our economic output, but far fewer than currently do. How will our economic system handle that situation? The selling of labor is the primary mechanism by which we distribute resources, but if we get to a point where only 20% of the adult population are needed in the labor force then how do we distribute resources to the remaining 80%?
Now, where things get really interesting is that "needed in the labor force" is not a binary thing, either. What if there's a big slice of the population from whom we only need five hours of labor a week? And they coexist alongside another slice of the population from whom we need forty hours of labor a week?
Maybe we're already a few steps down this road.
Most jobs that people have now aren't strictly necessary. If everyone gave up their leisure time to do all of their own cooking and cleaning, a massive set of jobs would disappear overnight. If we all at local, another. And the list goes on. Effectively, what happens is, we invent new jobs that are based on want as opposed to need. It's easy to look at that picture and say 'there is so much unnecessary work that happens!' but really, that X% of the economy based on want is required for price discovery of the rest. That is what your last paragraph is touching on, how do we decide who does what and how much? In capitalism, the answer is price discovery, and for that to work, everyone has to participate in the market.
This is precisely what I'm getting at. We've built a system on the assumption of a forty-hour full-time work week, with a goal of minimizing unemployment and (recently) maximizing labor market participation. We did this because we need participation in the market for effective resource distribution.
What happens when our economy simply does not need that much labor to produce all the economic output we want? Do we force people to continue participating in the labor market in makework jobs just so that they can have access to resources? To what extent are we already doing this?
But logically it would seem that should be: Everyone still has to work, but a little less than hitherto.
Now the question becomes, how much less?
Overall I agree with you: I'm not naive, nor am I a utopianist. I'm fine with more equitable. But we're so entrenched in the status quo that it feels like you have to talk like a revolutionary to get even a shred of "a little more equitable".
Edit: wait though what's a "post-scarcity" economy, anyway, concretely? I've heard since I can remember that we grow enough food as a species to feed everyone (and yet we throw tons of food out) - is that not a decent marker of being post-scarcity? We seem to have enough wealth in the US to be in neverending proxy or non-proxy aggressive wars against various groups of poor and largely non-white people - that wealth, used slightly differently, has got to be some kind of dent in all sorts of scarcity, no? I'm not writing this to attack you whatsoever; I'm genuinely curious. Post-scarcity is a phrase I've heard smarter people than me utter every now and then, and it only just occurred to me that I've never actually figured out what it meant. (I'll Google it now of course but I'd love to hear your perspective all the same. Cheers.)
The reason it gets brought up is because the moment one person's needs or wants infringe on another's, there needs to be a way to decide who gets what. Generally, this is what people are talking about when they talk about various economic systems. You come up with different mechanics that use the distribution of goods to incentivize the production of more goods.
The only way we escape the economic games that need to be played, to keep people working and producing things society needs, is if we no longer need them to produce anything. Then you no longer need the incentives and feedback loops that tie consumption to production, and people are generally free to do whatever the hell they want.
The idea of post-scarcity brushes over that dark part of human nature, and assumes we can figure out how to cooperate, even absent antisocial misanthropes. In Star Trek, they have "figured it out", but the transition to post-scarcity is understandably only vaguely described.
Things can definitely be more equitable than they are now, and should be if we truly want a meritocracy, but let's not get caught up in the delusion that society can exist without people doing shit jobs they don't like.