Either something is wrong with the social system which is making individuals to spend so much. Or something is wrong with the economic system, which is not providing enough income. Or something else wrong?
One of the middle class problems I do see is that owning your daily stuff (like a house and a car) - and hence gaining some measure of independence - is increasingly difficult, even for relatively high earners. I think another poster here got it right when they said that being upper class ultimately means being a rentier instead of a rentee.
The fallacy in this argument is assuming that if you cannot buy your own house and car, there is literally no other way to obtain shelter and transport.
I live in a big German city, though not quite in the city center. (My commute into the city center is 20 minutes by tram.) My monthly expenses for shelter and transport (not counting long-distance trips) come out to 500 € in total. With other non-negotiable expenses (food and insurances), this goes up to about 750 €. Rounding up a bit because there are always unexpected bills, a salary of 1000 € is the minimum that I need to live comfortably, if slightly frugally.