There is some discussion of this in various threads - but I think it is so significant that it deserves its own thread.

For years, one of the factors in determining upgrade priority within an elite status has been fare class - a Gold in a higher fare class would get upgraded before a Gold in a lower fare class. As of January 1, fare class will cease to be a factor/

Current Priority 2: Fare Class Groupings: higher priced fares are ranked above lower priced fares.

New Priority 2 as of January 1, 2024: Cabin Purchased (Original + Paid Upgrades)

The full list of the priority criteria before and after January 1, 2024, is here: https://www.delta.com/us/en/skymiles...%20the%20order