To the last point first:
Because nearly a century ago we could have lowered the working week to 15-20 hours per week, because mass automation became a reality. Right now the incentive is to use automation to weed out expensive labor, not to weed out labor. If automation were in the hands of a collective society to be decided on democratically, we have the technology now to eliminate several forms of work entirely, and most forms of work can be cut down to a few tasks. We don't do this because it's in the best interests or employees to buy expensive machinery to cut out the expensive work, and to keep around cheap labor until either that labor becomes more expensive (unionization, wages) or the machinery becomes cheaper. In addition to this, if we eliminate the rich, and the entirety of the parasitic class, then we need to produce significantly less. Couple this with the fact that in a post capitalist economy without the profit incentive, you also don't need to produce 3+ versions of everything (a shitty version, a middle class version and a rich capitalist version), you can stop doing planned obsolescence, and you can stop with each individual company making 3+ versions of the same thing, and we will have to produce a tiny fraction of what we already produce. We can the best version of the thing, people who genuinely care about it working on it, and distribute it far more efficiently.
Plus, we eliminate most if not all bureaucratic work. We can effectively cut our labor to a bare minimum while keeping our production very high, being more environmentally stable about it, and using significantly less resources. All of this spells out a very few hours needed per week per person. That said, people may well choose to work more than that.
Monetary compensation isn't the only type of compensation, if we eliminate money, there are still reasons other than a kumbaya togetherness to working, there are passion projects, labors of love, art and science, and as for the more... Undesirable work, incentives can be introduced, I suppose, but they don't have to be monetary. I don't have all the answers for that, but lots of people have done lots of writing on it.
And it is an entirely different thing to do mopping than to do brain surgery. It is not an entirely different thing to cook a meal and do the dishes. Again, someone may well have to mop, but that someone doesn't have to be systemically disadvantaged and forced to mop up for a living, or because they want a single luxury in life.
If you have no problems with social classes, then you and I have a disagreement at the very root of this thing, and I urge you to consider people like the disabled. My mother can no longer, where would she be in this social democratic ancap style society? Bare necessities and nothing else? Because that's what it seems like to me.