Besides the general scrolling performance issuet that is bug #215045, on https://www.elegantthemes.com/gallery/divi/ there is an additional performance problem I have recently discovered: hovering the screenshot "cards" (the images just below the "Full Website Packs" section; ctrl+F for that) in that page are slow as hell to animate on mouse hover, even on Wayland with triple-buffering. Tested on my desktop workstation with open source AMD Radeon R7/R9 270 graphics in the Wayland session, but the problem also was visible on Xorg and on other computers too. In comparison, it's butter-smooth in Chromium on Xorg, a bit laggy on Firefox on Xorg, fairly smooth with Firefox on Wayland. The Firefox bug report is https://bugzilla.mozilla.org/show_bug.cgi?id=1823474 where you can see some of their insights, if any might apply to WebKitGTK as well... If it's because of the shadows, it might or might not be related to bug #221738 as well. However, looking at the sysprof output, it seems to be related to pixman and cairo.
Created attachment 466130 [details] sysprof screenshot
Created attachment 466131 [details] sysprof capture