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)
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)