Fixing the Lighting Issue in The Sims 4
This solution worked for me and I hope it will work for you too! The darkness of the sims while indoors was really annoying and I couldn't get a decent screenshot of my sims. You can see that there is a ceiling light directly above my sims's head here....yet she is still dark. As you can see I also have the "baby glitch" as may others do. Waiting for a solution from EA on that one!
So this is my sim and my graphics settings were on ULTRA all around. My game ran fine with this, other than the lighting issue.
After playing around with each individual setting I was able to identify the problem (at least for my game) which was the SIMS category under Graphics Quality. As you can see in the screenshots above and below, once I changed my graphics settings to LOW for that ONE section only, my game still looks awesome but NO MORE BAD LIGHTING! YAY!