Why is it saying my photo stream is shutting down

Because Apple is shutting down that service. Look here for information about My Photo Stream shutdown -

Information about the My Photo Stream shutdown - Apple Support

tresa67 wrote:

Why is my photo stream shutting down

Because it is obsolete and has been replaced by iCloud Photos. See→Information about the My Photo Stream shutdown - Apple Support

Photo Stream was great while it lasted. A new photo on my iPhone would quickly be visible on iPad, and add itself to my Mac's photo library.

My 35,000 pictures are safely stored on local hard drives with back-ups.

iCloud Photos will never replace the simplicity of Photo Stream. It just gets in the way, and creates an added level of confusion when you manage your pictures on a Mac.

You are welcome to send Apple feedback.

No one here works for Apple. We can't change anything.

Yep; sent several notes to Apple.

Feedback implies a communications loop; in this case there's "feed" but they want to hear nothing "back".