Re: "Apple TV reduced the number of photos in their screensaver rotation from 75 to 12 in the past couple of days".
Thank you kindly for your questions. As Apple customers, just as you are, we can try to help, yet we can't modify Apple's software. The software generally works well in the way is it set up and documented, if we keep our OS versions up-to-date.
Wondering in what way you are selecting the photos you want to see in the screensaver ... eg: a particular album with the photos you want to see ... a number of individual photos ... a number of albums ?
Apple support's latest online article for tvos 27:
Use your photos as a screen saver on Apple TV 4K - Apple Support
Eg: says:
"Use your photos as a screen saver on Apple TV 4K
You can set the screen saver on Apple TV 4K to show curated memories, shared or personal albums, or photos from favourites or recent activity in the Photos app.
To "set up a screen-saver from the Photos App
- Go to the Photos app on Apple TV 4K.
- Navigate to Shared Albums or Albums at the top of the screen.
- Select a shared album from the Shared Albums category or an album from the Albums category, then select Set as Screen Saver and confirm."
We can ensure there is an album containing all the photos we want to see, ready for choosing.
To choose which memories or albums appear in the screen-saver
- Go to Settings on Apple TV 4K.
- Go to Screen Saver > Memories & Slideshows, then do any of the following:
- Choose which memories to include: Select Memories, then choose All Memories or Favourites.
- Choose which albums to show: Select Albums, then select Favourites, Activity or one of the shared albums from the list.
To adjust other screen saver settings see Adjust screen saver settings on Apple TV 4K.
and / or
"For more information on personalising and using Apple TV 4K screen savers, see Set up Apple TV 4K screen savers."
(ie:
You can create a special album for using particular photos as the screen-saver)
Else: If you want to communicate directly with those who work on the software, Apple provides a feedback website: (You can send bug reports, feature requests, etc.) Product Feedback - Apple