I've worked crappy jobs and never worried about getting fired. The crappier your job, the lower the threshold it's considered 'expensive' to replace you. It's not that hard to meet that threshold of contributed value. Employers generally have an incentive to keep you for this reason, unless you're truly terrible or something else is going on with their finances.

It's a little patronizing for you to assume I have no experience of being unprivileged just because our opinions about it differ. Or that those without privilege can't manoeuvre their way into choosing a slightly better job, even if they don't have an absolutely free choice over the space of all possible jobs, or even if they have to take a worse one temporarily in order to transition to where they want to be. Not all poor people are mindless cattle devoid of planning or agency.