>why would I adopt a philosophy that is so personally ruinous, demoralizing, and demotivating?

But why not be discontent with your reality? That's typically a sign to enact change and willingfully settling is an acceptance of how things are.

I think the problem lies in the way that capitalism treats companies and labour. Im not proposing we abolish capitalism but selling our time at a loss* to our employer doesn't "feel" good. Maybe you feel rewarded by your work and maybe you don't but you shouldn't destroy that feeling for the sake of complacency.

*Loss is possibly controversial, but an employer does seek to get more value out of an employee than they pay them.