Firefox appearance is custom and doesn't match system theme and widget set

I'm using Ubuntu 24 with the XFCE desktop. I'm installing the debs straight off packages.mozilla.org (currently 143.0.3). Firefox's title bar, and window manager buttons do not have the same look and feel as the rest of my windows. And I have no idea where they're coming from. They do change appearance in response to picking the different styles in Settings > Appearance, but the changes appear to be limited to colors only. The minimize, maximize and close buttons look differently than on all other windows, and they are more spread out than in, and the shade button is nowhere to be found. I'm attaching two small images, the first one is the standard set of widgets all other windows have, and the second one is Firefox's odd duck. I could not find anything in settings. "Extensions And Themes" shows that "System theme" is enabled. Well, it's coming up a bit short...