There's a collosal social difference between living paycheck to paycheck without any disposable income, thus depending on retaining your job to be able to keep a roof over your head, and being economically self-sufficient to the point where you are free to take multiple holidays throughout the year and even be free to quit your job and live off your savings through long stretches of time.

Middle class does exist, and it's existence is rather obvious. Trying to conflate middle class with low class or poverty makes no sense at all, because the plight of a low class worker has absolutely nothing in common to the problems and challenges faced by middle class workers.