I mean, I empathise with your problems, but this very much doesn't sound like "GDPR makes by side business impossible". It sounds like "exploitative user-data abusing ad vendor abuse s their lock-in to exploit people's personal data" kind of problem, so I'd say things are working.

FYI, "allowing EU users to opt-out" is still wrong, they would have to explicitly opt-in to targeted ads. At least, in so far as ads are targeted based on personal data.