I think there's a difference between them being a good company for customers and them being a digital fief. Similar to how Amazon could be seen as a "good" company by customers (return policy, cheap stuff, etc), but they essentially own an entire marketplace and decides who sells products, and extracts rents from people who are making good innovative stuff. Steam is the same way.
Of course, Valve doesn't have the mistreatment of employees Amazon does. They have no internal hierarchy, which is cool and I imagine means less management involvement. Their president seems to just want to make gamers happy, and thats great too.
Theyre an anomaly in the business world because they're seemingly a great company that doesn't follow monetization trends, while still being hugely financially successful. But they still extract rents from videogame makers, so leftists see that as a black eye.