What do you mean by lighting being added? You guys see nothing in game at the moment? XD
I mean making it more relevant. Shadows and light should have a gameplay impact.
...they do, dramatically. In underground areas such as crypts and caves, being in shadows makes it more difficult to hit both you and enemies.
Creating light sources via cantrips, candles, torches, etc dramatically increases your chance to hit.
Finding the sweet spot to create a light source that illuminates the enemies while remaining in shadow is a huge tactical portion of low-lit gameplay, and Darkvision is immensely helpful in combat, and seemingly in Perception checks.