The biggest issue is that the new Circle DOF does not function with TAAUpsampling enabled, meaning games that use Resolution Scaling effectively no longer have access to any DOF effects.
I previously reported this as a bug with a full demonstration project, and it was swiftly marked as a Non-Issue.
Prior to 4.23, users could fall back to legacy Circle DOF methods when TAAUpsampling was in use, which allowed at least an inferior method for DOF. However, 4.23 also removed the legacy Circle DOF algorithm.
So now you simply cannot have DOF effects if you use a Resolution Scale <100% and want to have TAAUpsampling for a clear image.
Note that ALL previous methods for DOF functioned perfectly with TAAUpsampling and Resolution Scale <100%.