when creating a shared folder Photos hangs

You are only allowed to share up to 1000 photos per hour. If you have exceeded the limit of an upload rate, Photos will pause the upload. If you have reached a limit, stop trying until the waiting period is over.

See: My Photo Stream and Shared Albums limits - Apple Support

Make sure, that all items are in a supported format:

These file types are supported:

• Images for My Photo Stream: JPEG, TIFF, PNG, and most RAW formats.
• Video and file formats for Shared Albums: MP4 and QuickTime file types, and H.264 and MPEG-4 Video file formats. Videos can be up to 15 minutes in length.

Then I'd try creating the shared album, and then adding the photos a few at a time. Perhaps start with 200 at a time and work down until it doesn't work.

Or you may find you are adding a particular incompatible file which causes the hang. Again, adding the files step by step will help you narrow down which one if this is the case.