How do I revert to the previous Messages app layout on Mac?

Was there a recent redesign of the desktop Messages app? It used to function similarly to the mobile version, with the "main" being a list of conversations with message previews. Now, it seems there is no way to have the app open without being in a specific conversation:

This makes it more difficult to navigate since there is no name provided. Additionally, not having a separate screen that lists all messages risks unintentionally sending read receipts just from opening the app (as I have already done, unfortunately). I tried looking through all the settings, but didn't see anything that would allow me to adjust the UI in a helpful way. Anybody got any tips?

[Re-Titled by Moderator]

Original Title: Desktop Messages app redesign?