> memorized magic numbers and not proper derived constants.
Metric units involve far more magic numbers than customary units.
The meter is the distance light travels in a vacuum in 1/299,792,458 seconds, so defined to preserve magnitude of the meter despite being originally based on an erroneous measurement of the circumference of the Earth, itself an extraordinarily arbitrary value when measuring things other than the earth itself.
The kilogram is currently defined as the mass of a physical standard, that being the master kilogram held by the BIPM in its headquarters just outside Paris.
If we want to redefine units according to Planck lengths or something similar, let's do so, but we'll of course end up expressing units that are relevant and useful in the context of human-scale experience in Planck lengths, and probably end up keeping the same customary (and metric) units.