There was still a pretty easy line between "I take credit cards" and "I don't take credit cards". The rules for PCI drastically vary between company size too, in that compliance for small companies is pretty easy, and your responsibilities increase as you go. To this day, there are companies that don't take credit cards too (though usually its not to avoid PCI, heh).
But yes, once there's an industry of GDPR auditors, precedents in lawsuits, and the threshold for "Do not market explicitly to europeans" is obvious and well understood, this will be much easier.
And still, until the end of time, there will be companies that aren't GDPR compliant and don't work with EU customers. Maybe with the goal of doing so once they have more time and resources.
It's basically a checklist, and you're either compliant or you're not. It includes various levels with actual numbers and explicit requirements, there's very little interpretation needed.
If anything, it should've served as the model for GDPR.
