Or you can just use Google Takeout: https://takeout.google.com

Deselect everything, select "Mail", create export, wait until it's done, and then download the zip.

Takeout is great for a total archive backup, but using it just to extract photos is where the UX breaks down for most people.

When you export Mail with Takeout, Google dumps your entire history into a huge .mbox file. If you have a 20-year-old account, you're downloading tens of gigabytes of raw text data, headers, and metadata just to get to the images. Once you have that huge file, you still have to figure out a way to extract and decode the image attachments from the raw email text.

Mail Memories just gives you what you want: the photos.