If we can avoid massive collective issues that would be appreciated as there is very little agency the individual has to address those and that helpless ess can often extend to the more solvable individual matters we all grapple with but also occasionally rise to conquer.
Well, fundamentally capitalism involves the deprivation of the means of subsistence and production from one class so that they are forced to sell their labour-power to the capitalist class in order to obtain the means of subsistence. You could define that as “mistreatment” or not I guess, but whether or not you do, personal treatment by your capitalist does not change the form capitalism takes. Workers’ power comes from combining. Capitalists are already combined—they work together to keep wages low and prices high. Unionising only levels the playing field in that regard.
I’m not saying that you should always focus on unionisation in every situation—sometimes there is more important political work to be done. But if you have nothing else to do, it’s often the most accessible starting point.