This is for anyone else who no longer sees the button to switch back to the old outlook. I have included step by step photos to get back to the old outlook!
First click "Help" at the top left.
Below "Help" should bring up another menu, now select "Feedback".
Now look to the very right and you should see the option to select a feedback option,
select "Report a problem".
Now you should see a box where you can type what the problem is, make sure to clearly mention that you cannot switch back to the old outlook, the button is missing and you want to switch back to the old outlook, this is important because when you submit this answer it will scan your message and generate possible solutions.
Once you've filled out the box with your problem, scroll down, click yes or no on both options (it doesn't matter what you choose but you need to select an answer for both), then click "Submit" at the bottom.
It will diagnose the problem and match you up with one or more possible solutions, make sure you see this one below that says "toggling out of the new outlook for windows preview", DO NOT CLICK "Yes" AT THE BOTTOM or it will end the feedback and assume you got your answer and you will need to restart this process. Instead you need to click on the arrow that is circled in this picture.
Freedom awaits, now click on "Do it for me" and it will automatically take you back to the old outlook. Congratulations! You've graduated from this circus of chaos and confusion. Farewell, and may your future endeavors be as comforting and delightful as a slice of warm, homemade buttered bread.
