I get exactly where you're coming from. As a website owner myself I understand the complications.
Maybe this is the point of GDPR. If you don't know how to control the data, or don't have the means to take responsibility for the data that your systems collect, you shouldn't be allowed to collect it.
Trying to fix this by blocking EU traffic is literally zero defense and if someone wants their data removed then they can't because as far as they know you don't exist anymore when they try to visit your site. It's not even like they can rely on the WHOIS to contact you to remove their data now. Your website is the means by which your previous EU traffic accessed your services, so to remove it from access to them and to keep their data isn't the right thing to do.
I'd suggest incremental steps to addressing it rather than a big bang like blocking traffic or deleting your websites completely.
Sadly just saying that you don't know how to do it doesn't help the situation for anybody.
Good luck getting your site sorted.