> This trend of countries declaring that everyone on the planet is under their jurisdiction if they mail something there (or respond to a network request) is bananas

I disagree.

Imagine I ban health potions in my realm. I am running a Darwininistic experiment to make my people the most resilient people of the world and I want them to succeed through survival of the fittest. I tolerate non magical medicine but anything else will pay 1000% duties or be confiscated. A merchant comes by with a delivery of health potions to "Johnathan Man". The guards point to the "Survival of the ssssttttrrroooong" banner, while the merchant throws a fit saying she has a very powerful uncle that just happens to be a known warlord. The guards laugh, close the gates and go back inside for another pushup context. Meanwhile Johnathan and the merchant complain things about jurisdiction to no one in particular.