Share auto created movie from memories in Mac

In Photos for Mac you can share the photos from the memory, but not the memory movie, see:

Share photo memories with others using Photos on Mac - Apple Support

If you want to share a movie, you have to create a slideshow project from the photos in the Memory, then export the slideshow as a video and share the video. The theme music will be different, and the Live Photos will not play, however.

To create the slideshow video select all photos in the memory with ⌘A, then use the command "File > Create > Slideshow > Apple". Set a theme for the new slideshow you like, select music for the sound track, then click the "export" button to save a video.

No. Tell Apple what missing features you'd like restored or new features added in Photos via Feedback - Photos - Apple.

However, you can use the Screenshot app to make a screen recording of the playing movie. Launch the Screenshot app, select record area, select the movie area, start the recording and start the memory movie. Save when done.