This is a strawman.
No one expects people to still do that for $10 an hour, that's not a lack of thought from people promoting UBI, that's the feature they want delivered.
The idea behind UBI (or another scheme that would actually work, anyway), would be that 1) you plunge your own toilets or 2) if you want someone else to do it, you pay them accordingly.
In such a society, your farmers, builders, utility providers, tradespeople and so on would likely earn more, and educated white-collar jobs would likely earn less relatively. This is already what happens in more limited subsets: devs that want jobs in an interesting sector like the games industry typically earn less than devs taking soulless corporate jobs like banking or ad-tech. Lawyers that work for NGOs typically earn less than lawyers that work for the above soulless corporations.
But it's okay for some people to just opt-out of work. Everyone else will want to do this work because they have an innate passion for it. (sarcasm)
Where I disagree with you is that I don't think this maintenance of a will to use opportunity and social obligation is worth more than the suffering of the people who are coerced by our maintenance of this necessity, or who fail to meet the demands placed on them and experience the consequences of that failure.
Yes, were we stranded together from Shackleton's Endurance hauling sledges, or adrift at sea rowing a lifeboat, or subsistence farming to eke out survival on a desert island, and everyone had to pull their weight or we'd all die, I'd pull my fair weight and I'd advocate for the expulsion of anyone who didn't pull theirs and in so doing imperil the entire group.
No, we are not stranded together in this way on Spaceship Earth. We have enormously greater wealth and resources than we require to sustain our existence. No longer does 90% of society need to devote themselves to farming wheat at 7 bushels per acre to provide bread for a himself and a small fraction in excess that with 40 of his neighbors' farms can support handful of non-farmers for his community like a blacksmith, a miller, a tailor, and a feudal lord. A single tractor can seed, fertilize, or harvest dozens of acres per hour, and achieve yields exceeding 70 bushels per acre. We merely have to distribute the value more equitably, even if the amount of that value is halved, quartered, or decimated by people opting out of the will to work.