I think all of us have worked a job like that at one point or another, but (I'm hoping) the rest of us didn't turn into morbidly obese troons screeching at the stars about capitalism. Jim's problem is he is an aggressively unremarkable man by almost every metric, and his frustration over this reality is what causes him to lash out at whatever he deems the currently appropriate target (feminism, capitalism, transphobia etc).
He is incredibly lucky to have found the relative success he currently enjoys --mainly thanks to stealing his sense of humour from old British TV shows and comedians-- because if he hadn't tripped into this pot of gold he would still be working dead-end cubicle jobs in prefab office buildings, since he is qualified for and capable of nothing else.