This page https://shol.ly/ethan/data/fantasy-sci-fi-word-count/ seems slow in all browsers, but it's especially bad in Firefox. I think it's mostly shuffling around a lot of data. One thing that jumped out to me when looking at the flame graph was the time taken up by js::ProxyGetProperty. https://share.firefox.dev/3SyPXBt
Alternately, using the dropdown just above the graph, try switching from "Universe->Books" to "Series->Books".
Build from Aug-2022: https://share.firefox.dev/458PaNn (4.7 seconds)
Build from today : https://share.firefox.dev/3OYFkYU (3.2 seconds)