Get in there and push back against China Bad propaganda.
/r/UrbanHell is one of the better places to push leftist messages on reddit. It's big (600,000+ subscribers) but most comment sections are manageable, and housing conditions/urban development is so fucked up in much of the U.S. that you can find a pleasant amount of support for public housing efforts, even in AES states. "These big scary AES states actually give a shit about their people" is also a great way to get people to question how scary leftism actually is.
Every sizeable subreddit sucks, and you're right that this one isn't much better. You do get comments calling this stuff out pretty regularly, though -- I've seen more "this looks pretty normal, actually" comments than I can remember. Take a look at the top comment on this post:
Leftists can make some headway there.