You can’t automatically set a channel to be marked as read, for example.
"Google Chat is now available in early preview for personal Google Accounts on Android and desktop. When you turn on Google Chat in Gmail settings, you can test the experience and features. You may not be able to switch back to classic Hangouts in Gmail settings."
-- https://support.google.com/chat/answer/7653601
Only giant monopoly profits can sustain decades-long incompetency like Google's messaging systems.
Hah yeah, Google has only spent the last, what, 10 years developing video chat apps? It just blows my mind what a dunpster fire their text and video chat app conveyor belt has been.