There's another option: 1. Morality of a society is not a single dimension. There are multiple aspects of life in which society could become more or less mora

There's another option: 1. Morality of a society is not a single dimension. There are multiple aspects of life in which society could become more or less moral, depending on what activists choose to fight for (e.g. exploiting other's labor) 2. The morality level doesn't have to go straight up, down, or be flat. It can move like a wave (or in some cases, a roller coaster), increasing or decreasing over different eras as people learn and forget the value they derived from certain morals.