Base 10 is a completely subjective concept as well. Why 10? Why not 12?
As far as those "subjective" concepts you are poorly satirizing, the reason they exist is because they are human-centric. 100f is "roughly" the temperature of the human body. A cup is roughly the size of your fist, etc. That is the value, not "the only thing" but THE THING. It is the reason the units exist!

A meter could just as easily be the length of my dick and a kilogram the weight of me balls, then we could create a whole system out of it and relate to all sorts of other arbitrary measurements based on water or an ideal hydrogen atom or the exact amount of time a carbon crystal oscillates in one rotation of the earth, or whatever. But all of those are so divorced from human's, you know the people who this measurement system is ostensibly for, as to be 100% arbitrary. Why do I care how long it takes light to travel from the moon and back, when I just want to buy a rope that I can use to tie my mule to a fence post out of range of my garden? I paced off 25 feet, so I'll take that length of rope please.
No I don't know what 833cm is. Please just give me 25feet.