You’re assuming. It’s probably not a good idea to base one’s website’s accessibility strategy on such assumptions. Headaches and eyestrain are a real problem for many people. For example, people turn on dark mode because they have trouble looking at white backgrounds late at night or early in the morning. The same rule probably applies to bright colors.
> Remove the design and you make the experience inaccessible to me. These are trade offs, not absolutes.
I don’t think trade-offs are necessary. The website can have a shrill design and be accessible at the same time. For example, if the website was compatible with the browsers’ reader modes, then users could view the site in a simple black and white design.