

That really doesn’t solve the problem, like every other Firefox fork they’re completely dependent on Firefox. You can’t just make a new webbrowser just like that, and while third party developers can certainly disable some anti-features, there are limits to that and they can definitely not do the basic work that the Firefox devs do (or could do, if Mozilla had different priorities).
At least where I live, it doesn’t make sense to kill spiders at all. There literally is not a single local spider species that you might encounter at home that’s even somewhat dangerous (AFAIK even in the wild there’s only one, and even that one usually won’t kill you). If there’s something that’s too gross for you, just pick it up with a glass and throw it out of the window (which is much easier with spiders than with flies). Spiders do kill flies and other critters that are annoying or even dangerous, so you definitely want the poison that kills flies but not spiders.