While this is true, most of the "opportunities" presented by PageSpeed Insights are things I have little or no control over, such as eliminating render-blocking resources and removing unused JavaScript and CSS. These improvements will have to come from you, though I imagine they would require insane amounts of work and are therefor not prioritized.
I know these numbers will depend on a lot of factors, but I think they speak of an underlying issue – not as in something you've done wrong, but something that's hard to "fix": When viewing the front page on my community, 77% of root_framework.js and 92% of framework.css is unused. When viewing a topic, the numbers are 74% of root_framework.js and 89% of framework.css. Given the required time and resources, these files and the rest of the scripts and style sheets could be massively optimized, which in turn will benefit everyone, especially mobile visitors.