The "cohesive narrative" stands alone. History exists only on its own terms. You cannot look at something that happened in history and say: we can do this because it happened then. It is not absurd, it is the basic aspect of how histography is taught in university (and btw, if you study politics...you will find the same idea, "path dependence"...you see parallels in every social science because it is a fairly common mistake made by people who haven't thought about the issue deeply...the "why don't you be like Denmark" meme is a classic of comparative politics).
I am not saying that the present is the only lens (again, you haven't even started to understand what I wrote). The point is that the present is the only present. The past can only be understood in it's own terms. You are not constrained in any way because the past provides only information about the past, not the present.
It is irrelevant whether yesterday is like today because history is not about yesterday. Again, if you are interested about this subject, I would read some books about historiography (EH Carr and Elton are two of the most important books of this last hundred years...but, again, I don't think you will find anyone arguing for the position you are taking because it so clearly is an attempt to justify a political position today...this isn't what history is, any political position today has to be justified in the terms of today...historical relativists do not take your line, no-one does, it makes no sense unless you have no idea what history is).