Looks like Excel’s error dialog boxes have finally been brought into the 21st century!
They now have a modern appearance and fit better with the Excel theme. It’s a minor change in the grand scheme of things, but a UI and UX advancement, nevertheless.
You’ll also notice the Help button that appears in some of the old dialogs has been replaced by a question mark next to the close button in the top right.
Have these come to your Excel version yet?