The contrast ratio for the body text is 7.57:1 (or 7.25:1 if the text is on the light grey background), which meets AAA accessibility standards (which is 7:1).
Body text isn't the issue I would think - it's various headers, downvoted and especially "dead" posts which are almost to read without selecting the text, even with perfect colour vision.
This is also in part because of human perception, i.e. it wouldn't be as bad if the rest of the page had the same level of gray for the text. Because it is not the case the darker parts suck your focus in. If you want people to actually read your text, that is a pretty stupid move and just shows how serious you can take all that spam on this page.