What version are you using?
Forge: 1.12.2-forge-14.23.5.2854
Dynamic Darkness: darkness-forge-1.12.x-0.4.2
Optifine: OptiFine_1.12.2_HD_U_G5
Texture Pack:
John Smith Legacy - Modded
Does this issue reproduce with the latest release?
Since 0.4.2 is the latest, yes
Which other mods do you have installed?
Optifine
What did you do?
Just add the mods and the texture pack and enter to a cave, you will see how everything is still visible
What did you expect to see?
A total Darkness

What did you see instead?
The minimum illumination

Additional Notes
well, this can be fixed by removing the lightmaps inside the texture pack, but if you manage to do it, it would be great to be able to use the LightMaps and still having that amazing total darkness of Dynamic Darkness.
i really like the red-ish effect of the light maps in that texture pack, but the effect of total darkness is more valuable, anyways having the best of both worlds would be amazing