This is what happens, when no one is maintaining software.
Security is more important that anything, certainly than having time or not to update your code.
You're 100% in the wrong here, and Google is 100% in the right, and I hate Google more than spammers, more than pretty much any other company there is.
They're not wrong here, and it hurts me to support their stance.
Fix your stuff. Stop blaming others. I doesn't matter why you're in the situation you're in, you're wrong to be there. No matter what.
If you think security is an afterthought, you're doing it wrong.
this also really highlights the problem with python's 2 vs 3 split: there is a large body of work that will never be updated and will forever run 2 including actual web/publicly facing code. And saying "just upgrade because security" isn't going get much of that code upgraded.
This sort of thinking, is why places get hacked. You don't know what the access vector is. Stop making excuses. Secure your shit.
I would be so happy if a law was passed, and such actions were criminal.