If you took a moment to think of use cases other than your own, you would realize that there's a lot of us that ONLY use facebook messenger. I haven't checked my newsfeed in ages.
They also didn't want to split the user experience of using Facebook messenger on mobile and hence the forced switch.
It was only a big deal because of the surface area of the world that the main Facebook product (w/ messenger) covers. I guarantee you that if Google did something like that no one would care (at least not enough to give 20,000+ 1 star reviews)
This reminds me of the talk "Is it really Complex? Or did we just make it Complicated?" by Alan Kay.
The complexity of the underlying problem, messaging, has not changed, but FB has made it a lot more complicated.