It also doesn’t cede more market power to CloudFlare, which tends to block non-mainstream browsers, users with adblockers, Tor, or cookies and JavaScript disabled.
This tool does block JavaScript-disabled browsers though. There's a comment here that complained about the pain Anubis causes with cookie-less browsers, but they got downvoted.
IP reputation will be subject to very high false negative rates because some unscrupulous bots have taken to laundering their traffic through residential proxy companies. There are alternatives to cookies like Etags, but they have their own issues.