Most importantly, why are users ok with this? It seems to go against world typography guidelines such as World Wide Web Consortium (W3C) and more. Developers either don't mind or they don't access these websites. I find Chromium browsers are the worst.
This bizarre unhinged mindset affects everyone. And no, it's not a vision issue — only morons would assume this. It's just not natural to look at light fonts on the screen.
This seemed to have started with Apple and the Mac more than a decade ago, then it spread everywhere.
While there are a few workarounds like font enhancers or high contrast themes, they don't always perform well or they interfere with images. Even this website is guilty but not as bad as many. Fortunately, I am using a font enhancer extension.