The binary break of "believer" and "atheist" is a terribly modern, Western construct.
Plenty of Buddhists & Daoists practice ritual and teach mythology without believing in supra-natural powers -- yet atheists wouldn't comfortably count them as their own.
For that matter, there's a whole spectrum of doubt and non-belief within Christianity and Islam. These people are part of the community of believers -- yet sometimes feel ill at ease with the label or the assumptions tied to it.
There are also people within atheist and humanist communities who have positive experiences with communities of faith. Who wonder if their unbelief is like color-blindness...not an illness, but a random variation in human experience.
One way of being, but not the only way.
Perhaps more than anyone, these people sense there is something "off" in the modern paradigms and the reactionary movements of fundamentalism.
Their narrative is neglected.
May they no longer be invisible--there's room for them at the table.