I have this exact same issue, and it seems to be related to the new update.
Minecraft launches fine and then in the Singleplayer, Multiplayer, etc. menu anything I click on just toggles the screen from full screen to windowed. It’s so frustrating. I also have a Macbook.
Natalie
@Jonatan Thank you, that was the issue! My toggle fullscreen button was set to the left click mouse button, I never realised.