the metric system is based on the physical properties of Earth

Not really. Official units are defined in that kind of way (a metre used to be a certain fraction of the circumference of the Earth, though it’s now a certain amount of time travelled at light speed), but the definitions are arbitrary and used to justify defining the base unit how we want it. Metric’s superiority has nothing to do with metres being better than yards or kilogrammes being better than pounds. It’s this part:

and base 10 counting

As well as the fact that derived units all fit together nicely.