How so? Not "people would" but only you would, if at all, because for some reason only you want to have different font preferences just for Forumosa.
And when they do that, they use the browser's default fonts? That would be Taiwanese websites written in Chinese only, right? Then there are separate setting for Chinese and Latin fonts in Firefox or, if it's not enough, browser extensions that can help, for example Tampermonkey.
It's perfectly fine to have your own preferences, just don't claim that a font change at Forumosa forces you to disable customized fonts for all websites because it's simply not true. The issue seems to be that you have an ugly default serif font set in your browser's preferences but don't want to change it for some reason and instead expect the websites you visit not to ever use it. I don't really understand what you're trying to do but it's a client (browser), not a website issue and I'm sure it can be easily fixed in the Settings, about:config, userContent.css or with one of the numerous extensions. Linux, if anything, offers more room for such customizations.
This has steered way too off-topic so I'll stop at this but it's just worth pointing out that none of this has much to do with the new Forumosa. If sunlight is too bright for you then wear sunglasses instead of trying to dim the sun.
Back on topic, I just hope the admins can at some point decide this and other issues in a dictatorial manner, according to their own preferences. Otherwise, we'll have never-ending discussions and design by committee.
It's not 79% of Forumosans but 79% of the 16 people who bothered to vote in the poll, by the way.
Edit: and it's down to 69% now.