That doesn't help with volumes of otherwise legit looking traffic right? The problem that Cloudflare and Akamai etc address is usually content that is otherwise static that can be cached. Say the front page of hot lemmy.world is updated every few minutes with the newest hot item. That page is otherwise distributed by the CDN so the CDN can just direct the traffic to access it, and no requests are made to lemmy.world.

nginx would be helpful for any attacks located from a single address trying to making large numbers of connections, but without reading more into the attack I can suspect that this isn't what the attacker did.