First Class Downgraded To Economy

Flying ATL-SFO tomorrow morning and when I went to check in, my first class ticket had changed to economy. Instead of 3A, I am now 37D. I paid full price for the first class fare, and when I call to Delta, they have no explanation as to what happened. They said they could refund me the difference of economy and first class, and offered 15,000 SkyMiles. Anyone else run into this, and does their compensation seem fair? My wife’s ticket was also downgraded as well, 3B to 39B.

EDIT: Thank you all for the advice. A quick update. Delta called me at 10:30 pm the night before the flight and offered accommodation on an earlier flight (8:05 am vs 10:55 am) in first class. The seats weren’t together, but at least it was in the class that we paid. An earlier morning Uber to the airport wasn’t as bad. They did refund the fare difference between economy and first class, provided us each a $300 ecredit and 15,000 SkyMiles each. Not ideal, but overall happy with how Delta handled it. I am disappointed it happened and as a VERY loyal delta consumer for the last 15 years, I will reevaluate going forward. Besides trips to Europe and Asia, I only book Delta flights for business and personal. Medallion member for years and both wife and I have delta reserve AMEX. Delta, if you are reading this, you are alienating your consumers from decisions you are making.