The blog post mentioned the attack that happened in June this year, so I don't think we can call it old yet. Which past incident are you referring to? If the same incident happened I wonder what measures were taken after the first incident happened then. On the other hand, I have read multiple cases where a mailing list provider got hacked, which shows that no providers are safe nowadays.
Yeah, this email list allows hackers to access a source of potential users who are highly likely to have crypto assets in the form of ERC-20 tokens. Using this email will save hackers a lot of money and time in stealing the crypto assets of their victims.
The danger is that hackers may share this information within their community, and hackers may use it to attack multiple times, especially during bullrun, when FOMO causes many investors to be blinded by fake information about airdrops or updates from MetaMask and CEXs. All investors should be wary of email attacks, especially in the next year, when the crypto market will be at its hottest!