For historical reference, the EU operated for many years with strong borders between countries, and without the Euro common currency.
IOW it stuck to the original goal, of eliminating trade barriers between countries, for mutual benefit.
All of the other crap came later, with adding poor countries, climate control, common currency, etc.
Sticking to the knitting of economic betterment, and no more, would be the preferred outcome.
People should not need rules and permission from Brussels to change their toilets or tires.