Thanks for the feedback! We are working on this.
Current Dark Mode support: https://docs.microsoft.com/en-us/officeupdates/release-notes-office-for-macAM commented
The reading pane in dark mode is the absolute worst. ! I love the dark mode for everything in Outlook except actually reading emails. No one designs emails or email signatures to be used on a dark background. What's next, making PowerPoint and Word backgrounds dark?