I do not even consider commenting on random blogs. It feels that got completely taken over by bots and shills and angry angry people a long time ago.
Upon further reflection, it's also about sense of community, or lack thereof - on social networks, I know who's reading my comments and I can engage with them. On blogs... I have no idea who else is reading it, I may never come back to see any responses, I may not care about anybody else's comments without context to put them in, so neither the incentive nor feedback loop are there for me.
(I may comment on e.g. Rock Paper Shotgun, but I don't consider it a blog - it's an online magazine and it has both the sense of community and daily return value. )