The mistake this country made when they first tried to "go metric" was trying to
teach everyone the conversion formulas. You don't need to know how many metric
whatsits go into an imperial doo-dad (the rest of the world doesn't know this
either). All you need to know is that a metric whatits is "about this
big/much/far".
Agreed. It was a big mistake.

Most people could only give a very crude guess on how much a gallon, pint, or
pound was if they had to measure out that much sand or water on their own. If
they can get about that good at guessing a kilo or litre, then they're good to
go.
That's a very astute observation. If the system were changed to metric
overnight, people would, by force of habituation, become as good with
metric as with imperial in fairly short order. Especially if there's
significant training in the workplace for those who need it.