This is the same reason I uninstalled the Facebook app eons ago. It got so bad, every 3rd post was an ad or a "suggested page" and the option to go to my preferred view (sort by most recent, friends only) was buried in 4 layers of clicks. I was able to get around this for a while by bookmarking the "most recent" feed on the mobile site but that now just redirects to the front page. I don't even look at Facebook any more, I just keep it around because I still get event invitations.
But of course, the developers are going to get the completely wrong message from this dropoff in engagement...