One problem is that the adaptive exposure will make every scene “reasonably lit” because the whole goal of the feature is to adjust to various lighting conditions.
To make unlit scenes be less well lit, and well lit scenes be more well lit, you can add an exposure compensation curve. Typically, I find that a curve with two linear segments, and a sharp-ish slanted breakpoint in the middle, works best – when you’re “below the line” you get darker lighting, when you’re “above the line” you get normal or brighter lighting. But other curves can work, too.
Exactly where you put the breakpoint depends on your particular world/art.
Also, it’s a little bit annoying to adjust these, because of the gradual reaction of exposure to changes. You may want to crank up the speed with which the auto exposure adjusts up/down, at least while iterating on the curve.
Or turn off automatic exposure entirely, set a fixed exposure level, and light all places of your level to match that setting.
Or add multiple post processing volumes, that change the exposure settings based on where the camera is at.
Or a combination!