I've disabled the entire notification stack on macOS and Windows 10 with some tweaks and couldn't be happier. It's not like I'm going to miss out on anything of value as Slack, Discord, Mail will just indicate new messages with a dock/taskbar icon change.
But it's sure as hell annoying to have unsolicited popups randomly appearing ("Java update available! Apple Music now 50% off! GeForce Experience driver update! Windows Defender scan results! USB drive not ejected properly!..."). They're also often embarrassing when screen sharing.
One thing that drives me up the wall on macOS is when an application demands attention and its dock icon starts bouncing... and doesn't stop. It happens over fullscreen stuff too.
The flashing icons in Windows are far less obtrusive, and I was just looking at the latest insider preview for 11 where they are making it so the icon will only flash a few times and then change the little "application is running" bar that sits under the app icon from white to red to indicate that it wanted your attention. Which sounds like an excellent way to handle it to me.
But it's sure as hell annoying to have unsolicited popups randomly appearing ("Java update available! Apple Music now 50% off! GeForce Experience driver update! Windows Defender scan results! USB drive not ejected properly!..."). They're also often embarrassing when screen sharing.