I have the same problem with the same (almost) workflow. I wanted to get away from the desktop ( and Adobe) and work mainly with the iPad Pro and Affinty, but apparently that doesn’t fit Apple’s vision: No import into iPad without going through Photos, and no support for something as basic as the desktop app’s “i” button in iOS.
The Affinity part of the workflow works better than I hoped but the EXIF/metadata black hole of iOS/Photos/iCloud Photo Library has ruined everything. Third party apps like Exif Viewer help, but again everything falls apart when the file goes back to Photos and iCloud.
I have to assume Apple is going to eventually phase out JPEG, only support its proprietary format, and eliminate RAW completely by making the workflow too burdensome. It’s not that Apple wants users to do it Apple’s way, they insist that Apple’s way is the only way.