Make the default to respond to the latest conversation not start a new one
When I open the app it automatically goes to a new conversation. It would be better if it went to the conversation for which I received a notification. Maybe make a + button for new conversations.
Lorentz Aberg commented
This makes tons of sense to me. The experience of Teams (i.e. the way messages are grouped and the way that new messages shift which items are presented as most recent) makes the natural desired behavior to respond to conversations, while the UI makes creating a new conversation the default and easiest action.
Simply defaulting the text entry to reply to the most recent conversation at the time the user has focused the screen and/or viewed a channel would make these two interests align. Starting a new conversation is the much less-common action, so I think it would be perfectly acceptable to put that action behind a button and/or key shortcut.