2 stars for effectively giving me the ability to put dark mode on any website.
-3 stars for
1) making all my tabs run slower...significantly slower
2) not honoring my preference of not running the addon on certain sites. After setting a site to not use the addon when I return to the page, the addon will still sometimes applying theming to the page...sometimes incompletely. This sometimes caused text to become unreadable.

A change could be made to the addon to correct this...default to off. Let me set a preference for if I want to apply dark mode or light mode, and then let me turn it on rather than force me to turn it off when it doesn't work for a site. This would default to the addon doing nothing on any sites until I explicitly say I want to use it there. You could even set it so I can choose whether the addon is used by default or not used by default. Options are always good.
I have uninstalled this addon because of these problems. If I hear these issues have been corrected, I'll try it again.