Earlier quoted context omitted.
"They're all like this so it's impossible to do good" is an even more morally bankrupt position. It rejects personal responsibility and agency, places you as the victim, and allows you to continue to be a bad actor in the world. You should change this.
It's not impossible to do good, that's not what I'm claiming at all, and that's why the last line is there. I'm pretty sure you can do good even within facebook, doing your utmost to keep the company accountable (from my experience in another big corp, we don't see 1% of what's happening inside it, and how many people are facepalming - and we'll never know if many things were just humans being stupid or actual calcul…
There are plenty of companies which can't easily be categorized as having significant negative effects to the world. You can work for a "bad" company but consciously constrain your work to a business unit which improves customers' lives.
What you're using is false equivalence. You know what the worst thing for the environment is? Being born. Why do people insist on living when everything is bad? Reject the notion that you're powerless to change things.