Low reading ability is not often spoken about compared to other impairments. Despite there often being an underlying condition such as dyslexia, there is a major taboo surrounding it. So most people with low reading ability will not admit it to anyone, let alone discuss it with developers.
It is in fact the most common type of impairment that can come up against barriers in games.
Aim for as straightforward language as your copy style allows, for example
“Click below to save your character”
“If you click below your chosen character preferences will be saved”.
Text should not be dumbed down, but length or complexity should be avoided if it is not required by the tone or to get the point across.
Keeping text as concise and straightforward as possible increases the likelihood of it being read by any gamer, but particularly for people who have a low reading age, for whom large blocks of text can be extremely intimidating.
More information: How to write in plain English