The new screen was a bit bluer than the original, so I turned on Night Shift 24/7 so I could adjust the color temperature. That seems to have been the main problem! I turned Night Shift back off and battery life has noticeably improved. I still feel it is less than it had originally been, but I also upgraded to iOS 16 right at that time as well, and it seems likely that the new operating system is partly to blame.
The ironic part of it is, I tried to research whether or not Night Shift can affect battery life, and all I could come up with was articles claiming that it can IMPROVE battery life!!!! Maybe that is true on an LCD, but I think the only reason it would save battery is by dimming the screen a bit (I can do that myself, thanks). It seems to me that it was constantly monitoring ambient lighting and tweaking the screen to match and therefore using more processing power than normal (but I could be entirely wrong).
So, I believe it was three minor things that added up to a very noticeable battery usage change
# The aftermarket screen is very likely not as efficient as the factory screen.
# Night Shift seems to have been using more processing power.
# iOS 16 is slightly more power hungry