There is nothing wrong with the metric (SI) system.
What went wrong was the US tried a
soft changeover.

Very few tried to learn to think in the
New system.
Wholesale and retail should have been prohibited from pricing in the old system. Period.
The could provide handy SI to US units conversion charts (BUT NOT PRICES)
This would make the people
do the math. Pretty soon, they would give up doing the PITA conversion.