This is your opinion and I would suggest not a very popular opinion at that. I imagine the vast majority of the world can look at the number of violent crimes t

This is your opinion and I would suggest not a very popular opinion at that. I imagine the vast majority of the world can look at the number of violent crimes trending down over time and use that as a data point to rank eras. Similarly extreme poverty rate since the industrial revolution has drastically fallen. Another metric that I imagine the extreme vast majority of the world would find a useful metric in ranking eras. There are plenty of other metrics to rank eras that make plenty of sense if you look for them, and why shouldn't we? Is it even possible to make progress if we're not defining what progress looks like? Is progress such a ludicrous goal for the human race? If progress is a reasonable goal and you can't make progress without defining what progress looks like then it's necessary for progress to have metrics that can be used to rank eras.