I made my own with Stylus. At its simplest it's 2 lines of CSS which pales in comparison to what Dark Reader is going with, and then I have one section for exempted websites, and two sections for websites I use a lot that needed specific small fixes. It uses basically no resources, and doesn't slow anything down.
The one downside is that because it uses CSS filters, some colors become less brilliant. This is a known flaw with how CSS calculates colors for hue-rotate
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