[niknetniko]

I don't get what this means?

- There an option to compress images before uploading (which is probably on by default). Not unreasonable.

- Content is deleted if you do not access Google Photos in any way during two years AND do not have a paid storage plan. Not unreasonable.

- If you use more storage than you pay for during two years, content will be deleted. Again, not unreasonable.

I really do no get the complaint here.

[Rygian]

I upload my pictures with quality q=X.

The next day I download a picture. Quality is q=Y, where Y < X.

One year after, I download the same picture. Quality is q=Z, where Z < Y < X.

So my pictures uploaded to Google Photos suffer from decay, whenever Google chooses to degrade quality.

None of your "not unreasonable" scenarios are involved.