That is something that happened a couple of months ago. If your photos were affected, they would have been deleted already and you should have received a warning well in advance. See the following from Information about the My Photo Stream shutdown - Apple Support
My Photo Stream is scheduled to be shut down on July 26, 2023. As part of this transition, new photo uploads to My Photo Stream from your devices will stop one month before, on June 26, 2023. Any photos uploaded to the service before that date will remain in iCloud for 30 days from the date of upload and will be available to any of your devices where My Photo Stream is currently enabled. By July 26, 2023, there will be no photos remaining in My Photo Stream, and the service will be shut down.Â
My Photo Stream was a service that was not the same as iCloud Photos. It was one method that could be used to transfer photos to other devices. See the following description from the same support article:
My Photo Stream is an iCloud service that originally launched in 2011. It temporarily uploads the photos you take on one device so you can view them on any other device with My Photo Stream enabled, and import them to your library on that device if you like. Photos remain in My Photo Stream for 30 days — up to 1,000 photos at any given time — and are then automatically deleted from iCloud.