We’re currently working on defining a compact mode experience. I will post more details when we have more to share.
I agree. The Teams UI is wasting a lot of space. More content could be shown per space, while still providing a clean and easy-to-handle look & feel.
Actually, some of my team say that it's hard to follow conversations, especially because so less content is shown (and they are forced to focus on the Teams window to scroll up or to expand messages).
This is one major reason why my colleagues (dev team of 20) want to move to Slack :(