I just think it's boring that you think money is the only reasonable motivator for these people. There are other forms of compensation and appreciation. And it's not the only option available to us. It's crazy to me that people understand the idea of countries that have military conscription but can't fathom the idea of a system of workable civil conscription.

As I see it you successfully identified a problem and a solution, but that does not suggest that that is the sole or even best solution.

When you do your scaling you need to scale everything. The adult population of the US is estimated as 266 million people as of now. Half a million is roughly 1 adult in 530 people. Let's quadruple it up so they have nice relaxed works schedule. Let's say now you need 4 people per 530. If you think you can't find 10 out of 1000 people who would do some sanitation work, with no stress and without having to think where their next meal comes from, you just never met people.
And this is the most important part that you seem to ignore - when people's basic means are met, they want to fulfill higher levels of Maslow's hierarchy of needs. For some that means doing arts or doing some engineering or running a company. For some, and there are s many of those some, that means "it's not much but it's honest work". Doing small visible changes that make the world the better place one picked up piece of rubbish at a time, is exactly, precisely what significant portion of humanity will be doing.
This also works in another direction: billions of people who would be doing something grand and moving humanity further, are stuck in mundane repetitive broken jobs they hate, because they're stuck in this cycle of needing to grind to survive, without having a moment to breath, which slowly kills every bit of light they once had a potential to have.

I think what causes this imbalance is human nature and our insatiable desire for more that is contrasted by the demand for convenience and ease. Not saying that I have a solution but that’s what causes this need for the motivation you speak of, in the form of money/power. And with an entitled human population that is unwilling to let certain demands go, and the willing few who would sell their convenience and time for a profitable venture, which others have deemed a mental illness (a desire for money).

Uncle worked down at city dump. He loved it. He was kind of a garbologist in a way. He was fascinated by all the things folks threw away. Retired there too. Got a job right out of high school and worked until he was 62 and retired. Dude has so many "trash" sculptures. That is to say, sculptures made out of trash. I think you'd be surprised the jobs folks enjoy doing.

For example i doubt that many people enjoy working at garbage disposable or basically any waste disposal

Ehhh I bet you'd be wrong. Only anecdotal obviously, but at practice and games for the kids, a lot of dads just chat when there isnt much going on. A couple of them work for the local garbage company. One of them commented that he doesnt know how I stay inside and work all day, he really enjoys being outside with the trucks in the morning, then enjoying the afternoon outside with the kids. Another one is a mechanic for them, he always thought the trucks were cool, and he still enjoys working on them (though he will 100% tell you, in great detail, which manufacturers suck for various parts). Haven't talked much with the last one about work, I think he is the only one just straight up doing it for money though.

And who knows, maybe the guy who likes being outside says that to be positive about his choices in life, but I see him at the park with the kids a lot, I've run into him heading out to the trails on his mountain bike, etc, so I believe him that he's perfectly happy doing it.

Automation for unwanted tasks is great though, I agree, and where automation should be focused.

I met a guy last week who was unusually passionate about water filtration and wanted to make a business globally. People are wonderfully weird.

Don't you think there is some way we could structure society to counteract that without creating an underclass of wage slavery?

That's absolutely not what bystander effect is, not even close. It has also nothing to do with the issue at hand. Bystander effect caused not by not willing to put an effort, it's incredibly complicated, layered, and not exactly explained, but probably the only thing we know about it for sure is that it's not because people are lazy

"Who's gonna do mindbraking soulcrushing jobs for days without a break?" Nobody, that's not a job that has to be done this way. "But if we stop orphan crushing machine, what will crush all the orphans?"
When you're imagining the worst parts of the worst jobs, remember that the reason those jobs have worst parts is because the main incentive of every job is to have the profit of a job as high as possible, and to exploit the workers. Yeah, some jobs are hard, some are complicated, some are dirty, some are all three. But all that is something people can and regularly enjoy. People don't enjoy when it's degrading, when it's soulcrushing for no reason, when there is obvious injustice. And it has nothing to do with jobs

Someone who wants to live a life of luxury and comfort in a world with wastewater treatment plants, knowing that everyone else is also pitching in and doing their part.

Someone who wants to live in a world without billionaire pedophiles in power doing nothing but hoarding all of the wealth.

Someone who cares about the wellbeing of their community and is motivated by that, rather than by selfish greed.

In other words, anyone. Everyone.