You couldn't opt-out of WHOIS (some TLDs just didn't allow for WHOIS privacy / proxy registrations) in the past, and it's IMO quite a hard sell that the public interest in the historic WHOIS data of some personal website should have any weight at all in this case.
Since the information was committed knowingly and willingly to the public domain, though I do not know much about it to begin with, I don't see how GDPR applies at all.
You could IMO also make an argument that the collection and scraping of WHOIS data without consent was unlawful processing as a whole, as the data was not provided to the domain NIC with explicit consent for third-parties to collect and save them forever, which would even make any overriding legitimate grounds for processing moot.
17a may also apply: The reason for WHOIS is to find out who owns a domain now, right? There is no version history. Historical WHOIS data does not serve this purpose anymore.
It's quite the can of worms.