How can I customize my current iphone lock screen and keep the current photo?

i just updated ios 15.7 to 16 and would like to customize my lock screen/wallpaper, eg. choose a different, less bold font for the date & time.

however, trying to customize my current wallpaper only gives me the option to add a new wallpaper. neither directly from the wallpaper (by holding it), nor from settings > wallpaper > customize i can customize the current one, it only gives me the "add new" option. and adding a new wallpaper cannot "copy" or port the current wallpaper as a template to a new one to start from.

My current wallpaper is a photo that is no longer in my photo library. I just want to Customize the current wallpaper, and it doesn't work, ADD NEW is what comes up when i click Customize.