I think you are probably correctly identifying their argument. I think there's no contradiction between recognizing that there's little you can do about national and international matters, and being concerned for the welfare of those you can actually help, among your friends, neighbors, and community. That's not "I've got mine," but as the prayer puts it, "the wisdom to know the difference."

Most people who worry about “systemic injustice” do nothing to change it. They just enjoy whining online to the benefit of no one.

My feeling is that the people who don’t pay attention to online fads are the people most likely to do good and right wrongs where they can (within their direct community) instead of the people that complain perpetually online about global events they can’t do anything about.

"But not everybody can just ignore systemic injustice and not try to cause change, however small."

Its also that, the majority ignoring what "they cannot change" at least directly, is a part of the problem. The majority really should not be "OK", and also able to say they do not condone the more horrific injustices. The majority can change the supposed systemic issues, they don't.

The OP in this instance (not the article) makes reference later to the "wisdom to know the difference", which is merely another way of saying, they are unwilling to rock the boat because they are too comfy to do otherwise. The argument about personal family etc., while true, is tangential to the point that you should not be "OK" - OFC everyone must put family, friends first, and crucially _once those are stable_ you can affect the most more change more broadly, not sit on your hands and say "I'm fine".