Why can't I ignore it? I have european customers but they chose to sign up with a business in a foreign jurisdiction where their laws don't apply. If it's a problem, the EU can feel free to block my sites, but I can't see how it's negligent to not comply with laws that don't apply in my country.

I don't comply with laws from many other jurisdictions either. Should I start applying censorship laws for China and Saudi Arabia too? Why should the EU be special?

I answered your question the first time. The answer is no. If you really had to ask this, just google "does gdpr apply to non eu companies?"

There are thousands of laws on the books where nothing happens when you ignore them. Sure it is possible that the EU will pick some obscure small company doing boring business things outside of the EU to make a test case out of, but how likely is this?

Anyone not up to shady activity can afford to wait for the case law and best practices to settle before doing anything.