i have the same issue you have, bright screens are the worst (i hated visiting wikipedia). try this addon in firefox. instead of messing with the colors and the contrast of the page, it rather puts an dark overlay over the entire page, reducing the brightness and preserving the look.
https://addons.mozilla.org/en-US/firefox/addon/dark-mode-screen/
well see now I am in a pickle. Do I go to the webpage that does not allow itself to be accessible and lose a day of my life to drugs and bed. or just keep using what I am using.