Why has this issue never been adressed? Dark materials are leading exposure to over react, thus making the auto exposure system unfit for many situations, especially when speaking of open world.. Exposure in photography is based on illuminance values which is independant from albedo of the scene. Light buffer is the closest information we have to illuminance. Average probes information could be used as well but might be less reliable.
This is a key feature missing on the engine IMHO.
I understand that Unreal engine rendering pipeline is not using any light Buffer except for debug view purpose.
But, in theory, by dividing the image buffer weighted average by the baseColor one, you could reconstruct the average illuminance in order to drive the exposure in a much more accurate way.
You could even propose a lerp balance between full Luminance based exposure and Full illuminance one.