I’ve had the same issues with Twitter and Pinterest feeding me intermittent fasting or other diet app ads consistently! Now on Pinterest it’s some awful makeup scam where it’s obvious that a blurring tool is being used in the video to make it appear as though all “imperfections” have disappeared using it.
As you say, it boils down to really lax and loose policing. I’ve seen people proactively report offensive content only for Instagram to feed back that it doesn’t meet the criteria to be offensive, even when it’s blatant. When very obviously harmful content isn’t even being pulled down, it’s no wonder they’re not considering the more nuanced pieces, especially as you also add, when they have commercial motivations.