You're not wrong. The OS does make it possible for the app to do things that are problematic, though (the facebook messenger head bubbles, whatever they're called, that can obstruct other apps, for example). Gnome notifications are relatively unobtrusive, they can only appear in one place (though I don't like that they can obstruct other apps), and there isn't a culture of every app thinking they have to interrupt you multiple times a day.

It's a team effort, I'd say, though facebook is where I lay most of the blame. I'm just ranting in general about the state of notifications and how insistent and entitled so many apps have become on many platforms, not really calling out specific operating systems or developers (though all the notifications I was complaining about in Windows were from Windows itself and not facebook or the like, so we have to lay all the blame on Microsoft in that case).

Edit: after thinking about it, I don't think the OS should impose good taste (eg to prevent Facebook messenger head bubbles from being really annoying and obstructing other apps), since that would mean apps that legitimately need that ability wouldn't be able to do so. I'd guess Twilight, a blue screen filter app I use and like, wouldn't be able to do it's thing if Android didn't allow apps to operate on other apps display. Facebook just needs to stop being so obnoxious.