Internet Archive is continuing to face DDoS attacks after several days, says “this attack has been sustained, impactful, targeted, adaptive, and importantly, mean”

Without knowing how, not really. If it's a massive multi-device botnet, like Mirai, for example, that's millions of indvidual devices across millions of addresses, so it isn't so simple as just blocking a domain. Trying to block all of them might well just block legitimate users.

Request limits also wouldn't work if it's millions of devices making a few requests at once, and an overall limit would have a similar locking-out effect as blocking everything. Especially if the DDoS is taking up most/all of that limit.