Although I do not have any personal experience with the program, MetaImage seems to be what you are looking for. From their website:
Metalmage for impeccable metadata
MetaImage is the only macOS tool that allows to edit, read, and write
metadata while working with all types of tag formats. Navigating
through a sleek interface, you can change everything ...
To reframe you question, you need to understand what Photos really is.
It is essentially 3 things :
previews you can look at on the screen
your originals sorted somewhere (including EXIF information, related to the shooting, and possibleIPTC information, vulgarly referred to as "metadata" )
a database to handle the previews
The database does not ...