That’s all totally valid.

My pet peeve is when people talk about the old king’s-body-part systems, as if they are the dumb old opposite of the new, logical metric system. That’s not just false, it’s ludicrous. Ya know, because the one system grew directly out of the other. They were never actually in opposition, as concepts. The SI progenitors just wanted everyone to be on the same standard, worldwide. And for that standard to be more perfect, more consistently defined, and continually improved upon.

In truth, the real step forward is the stubborn persistence of the international organizations that have worked across language barriers and times of international conflict to keep the system going.

And, of course, it has to be remembered that all that effort wasn’t worth doing, until very recently. Up until we had really fast mail (and then telegraphy/telephone) systems for communication, extremely interconnected and fast trade routes between essentially all nations, and extremely advanced cooperation among cross-continental scientific organizations, it didn’t really make sense to try and put everyone onto the same unit system.

In other words, the SI system came along when worldwide conditions were ripe for it to prosper. That’s not taking anything away from the aforementioned grit and determination and labor that the SI founders and current organizers have done. I’m just saying that it’s incorrect to characterize the situation as “gee, people were soooooo simple and dumb and gross, before these amazing French dudes saved us from our primitive inches and feet.”

And yet that’s how people talk about it. Like I said, it’s a pet peeve.

EDIT: Also, I think a lot of people fail to recognize that all the powerful nations in the pre-SI world had completely functional systems of standard measurements. It’s just that those systems didn’t function outside of their specific nations/empires. Again, there’s too much of a hyper-grandiose narrative, as if these French giants came along and invented ALMOST THE WHOLE CONCEPT OF MEASURING STUFF, overnight.