Stop Photos App From Creating Memories Automatically

You cannot disable it, only complain to Apple with a feature request.

Feedback - Photos - Apple

However, you can reduce the amount of memories that are created over time. Whenever a new memory is created, block it before you delete it. Then no more memories of the same type will be created.

See: https://support.apple.com/en-gb/guide/photos/pht96259d626/mac

Delete or block a Memory movie:

You can block specific types of memories whose content you don’t want to see. 

1. n the Photos app  on your Mac, click Memories in the sidebar.
2. Double-click a memory that you want to block.
3. Scroll down and click Block Memory, choose the type of memory you want to block, then click Block.

As you block more and more types of Memories, you will see less Memories created .

And you can disable the creation of Holiday memories. Photos > Preferences > Memories: Show Holiday Events

And refrain from feeding Photos with information. Do not name faces, do not take photos with GPS tags, etc. there is no way to disable this feature.

You can also block the memories in Photos iOS. Just block each new memory, before you delete it from your iPhone.