UPDATE: We appreciate your feedback on this thread and have some updated information. The game play area on public games remains the same size as the enhanced version was before the rollout of Theater mode for our Members games. That is, it takes up 2/3 the size of the screen.
With the change, you no longer have to click on an icon to make the screen bigger, because it already is the larger size (about 12% bigger than the previous smaller default size).
Some had other issues with the game play area change and we apologize for the inconvenience. We have been able to help many through one-on-one conversations and are happy to try to help you.
Please provide your operating system, browser type and versions (Chrome, Firefox, Edge, etc.) and a couple of screen captures to show us what you are experiencing. We will do our best to help you get back to playing your games.