Just try https://www.youtube.com/ in light mode, then switch to dark mode. Hope you will understand. Browser addons do not work well for webpage dark mode - colours, etc.
Unless I'm wrong, initially --and probably still-- the preference for dark mode instead of light mode is to reduce eye strain, as you've established on your very own opening post, as well as Cantsay here, as well as to reduce glare [flashbang, anyone?] when accessing apps and platforms during bed time when our eyes already adjusted to the dark of our room.
So, if your concern and needs are based on those two initial reason of dark-mode preferences, there is little to zero sense on arguing specifically designed dark mode by the web developers because it feels like "pro". I don't think most people here "love" dark mode for aesthetic reason. They simply doesn't like being blinded by the sudden burst of brightness. Simple as that.
I use the "default" light theme on my tablet and laptop [though I rarely access through my laptop] and have my android phone force set dark-mode that let me experience the forum as what depicted by libert19 because more likely than not, I won't access the forum through that tiny screen unless I really have to, meaning I only use them if I'm the road and didn't bring one of my tablets or laptop, or when I'm ready for bed and got notified for something interesting by the notifier. And that dark mode works just fine.
