The results are about what you'd expect, given dwindling PC sales -- most folks can't be bothered to upgrade because they've switched to mobile for their primary device. Firefox reports that 45 percent of people are still running Windows 7 with less than 4GB of RAM and a large majority have Intel CPUs with two or less cores. Few care about pixel density, as the most common display resolution is 1,366 x 768, driven by on-board Intel graphics, not NVIDIA or AMD discreet GPUs.
Top selling PC games, including League of Legends and Overwatch, can already run on low-spec PCs, so developers are likely well aware of the (terrible) average configuration. As Firefox points out though, there's much less information on WebGL, Flash (ugh) and other web-based gaming engines. Mozilla may want to heed its own report, as users often complain about browsers like Chrome and even Firefox itself slowing down their computers. If you're concerned about the privacy aspect of the report or want the raw data, Mozilla has a detailed Medium post on how it collected the data and where you can go to find it.