I can’t see the big deal. We use the Facebook SDK specifically for the free analytics. It’s just a default part of the SDK. It’s not sending anything any other analytics package wouldn’t
But the where matters as much at the what; sending it to FB means that they add it to their profile of your users.
Uploading all of this data to Facebook just so you don't have to run a Matomo instance (or whatever controlled analytics platform you use) is either laziness or disregard for your users. There's a reason the analytics are free and sacrificing your users for something this small is exactly what is wrong with the modern software ecosystem.