Anubis has a 'slow' and a 'fast' mode [1], with fast mode selected by default. It used to be so fast that I rarely used to get time to read anything on the page. I don't know why it's slower now - it could be that they're using the slower algorithm, or else the algorithm itself may have become slower. Either way, it shouldn't be too hard to modify it with a different algorithm or make the required work a parameter. This of course has the disadvantage of making it easier for the scrapers to get through.

[1] https://anubis.techaro.lol/docs/admin/algorithm-selection