I don’t follow the analogy. These are different types of alcohol. Neither is spectacular.

The old agreement included the old terms. There’s no such thing as upholding an old agreement under a new set of terms. That’s just a new agreement.

Is the analogy that the person probably won’t mind a slight decrease in quality because they are already drunk?

Maybe the drunk analogy was dumb. I mean practically no ToS in existence has language saying “these terms are set in stone forever and will never change.” Rather they generally stipulate that the terms can change given some kind of reasonable notice period.

This can be done without breaching any existing agreements if whatever being offered under new terms is a commercially-equivalent substitute for the old thing (such as switching from a Mohammed login to a Microsoft Account)

> uphold the old agreement under a new set of terms

If they change the terms its no longer the old agreement.