I am not commenting on the well-being of people working in fast food. Just on the availability of work. Whether such individuals can afford housing is totally beside the point of my comment.
Of course much of that drop is also demographics; the baby boomers are starting to retire en masse.
Still, the illusion of job abundance does not hold.
In fact the unemployment rate is low because the economy has produced an extraordinarily vast number of jobs. In May alone the US economy nearly produced a million new full-time jobs (solidly contracting the part-time count). The full-time job count is at an all-time record high. The US economy has produced 14 million full-time jobs in just the last six years. [1] And the median full-time income in the US is about $50,000, among the highest on earth.
> notice the record numbers of homeless on the streets?
The US homeless rate per capita has plunged dramatically and is at an all-time record low. [2] You're entirely fabricating your claims, both about jobs and homelessness.
The total homeless count has declined by roughly 27% in just 13 years. From ~760,000 in 2005, to less than 550,000 for 2018. The US added about 10% to its population over that time simultaneously.
How is that possible? Everyone knows the US sucks and has no safety net or support systems. Except, that's a lie. The US welfare state is now more generous than either the Canadian or Australian welfare states. [3]
[1] https://data.bls.gov/timeseries/LNS12500000
[2] https://endhomelessness.org/homelessness-in-america/homeless...
[3] https://www.bloomberg.com/view/articles/2018-05-16/the-u-s-s...
About the last part of your statement though: society has already implicitly accepted the crappy minimum living standards (at least in the US) that it's willing to accept. That doesn't make it right for the people stuck having to live according to that minimum.
Like c'mon. Working for less than a livable wage is just called making America worse. It would be much more productive to kill yourself and reduce the leverage employers have over the proletariat.