Anubis's design is copied from a great botnet protection mechanism - You serve the Javascript cheaply from memory, and then the client is forced to do expensive compute in order to use your expensive compute. This works great at keeping attackers from attempting to waste your time; It turns a 1:1000 amplification in compute costs into a 1000:1.

It is a shitty, and obviously bad solution for preventing scraping traffic. The goal of scraping traffic isn't to overwhelm your site, it's to read it once. If you make it prohibitively expensive to read your site even once, nobody comes to it. If you make it only mildly expensive, nobody scraping cares.

Anubis is specifically DDOS protection, not generally anti-bot, aside from defeating basic bots that don't emulate a full browser. It's been cargo-culted in front of a bunch of websites because of the latter, but it was obviously not going to work for long.