As someone who's marketed consumer apps to iOS users (with in-app purchases) - you speak the truth.

One freemium iOS app I worked on did nearly 5X the revenue compared to its Android counterpart (others were at varied-but-similar multiples). I imagine the ad-supported business would reflect the same - the iOS audience is just too lucrative for advertisers to ignore.

edit to adjust multiple. I went back and looked it up.

I would just stop using Facebook Messenger rather than use it in the browser.