agreed. an implemented dark mode which applies all over and in all drop down / right click menus and maybe a few sets of color themes/customization would be indeed nice and beneficial.
I tried a few addons, Gentle Night Mode and Dark Mode
Both are good, but could be better.
There is one i have to try yet, but it looks promising (Midnight Lizard)
Also using stylish extension with a global dark theme
So far i haven't really settled for any of those. Still trying and testing.