Almost all countries require official authentication to activate a SIM card. This seems to me as a huge privacy problem, if the country can track sim cards across cell towers and connect them to a person. It seems like a dystopian system, that we litterely can not hide from our governments without turning off our smartphones. It seems incredibly unnecessary to me and just sets up the system to be abused.

Or do I understand something wrong?

What can we do against this? There are some sim cards that can be bought second hand, but they will not be a long term solution.