this generally isn't how designing with cognitive or neurological disabilities in mind works, we don't want the user to have to make adjustments in order to use a website as this only creates more friction. Not to mention the fact that we don't assume that the user is knowledgeable on how to make those adjustments, especially with the senior population which is a large segment of the cognitively impacted population who are using the internet.

unlike with the blind or low vision population, those with cognitive and neuro issues often aren't aware of assistive tech, often aren't familiar with the accessibility settings on their devices, and sometimes aren't even aware of the disability they are dealing with and are undiagnosed.