You did not answer if there is a way for you to know that you have unread messages, with a Tray I can just look and see if I have unread stuff on Slack, or an unread email or maybe updates pending. And yes I can remove the System Tray if I don't like it for some reason or I can hide some of the apps in it. Long time ago when I was working on cross platform desktop apps the toolkit Qt,Net or Adobe AIR would handle the Tray for me, and the menus , I did not had to write specific code for Windows,Mac and Linux. What GNOME devs did is ask app develoeprs to screw the standards and write GNOME specific code, even GTK devs got rude answers from GNOME devs, this days GTK is GNOME only toolkit from GNOME POV.