Why has shared albums disappeared when I try to share a photo in 13.1.2 and how to I get shared albums on the iPhone. Why are apple improvements not improvements.

Shared albums should work like before in iOS 13.2. Are they still turned enabled in the Settings?

Go to Settings  > [your name] > iCloud > Photos, then turn on Shared Albums.

https://support.apple.com/en-gb/guide/iphone/iph3d2676c9/ios

1. In Photos, tap a photo or video to view it in full screen.
2. Tap , then tap Add to Shared Album.
3. Select an existing shared album, or create your own.
4. Tap Post.