How darken text for readability on a MacBook using Safari or Firefox?

When I was using Sierra, I installed Andika in my fonts, and forced web pages to use Andika. Unfortunately, that isn't enough in Mojave.

Apparently we're supposed to increase contrast. I also get migraines from the animation, so I also need to reduce contrast, which isn't possible, and especially not at the same time as increasing contrast.

This is a partial solution: https://dev.to/mrahmadawais/onedevminute-fixing-terrible-blurry-font-rendering-i ssue-in-macos-mojave--lck