Why are shadows so bright in closed interiors?

Development Rendering
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3
  1. You could bake the whole scene with CPU/GPU lightmass.
  2. Have you tried an “PostProccessVolume”, in there you can change almost everything regarding effects/colors.

If you want performance and doesn’t use anything like GI or Reflections you could look into Forward shading. It’s has less support, like MSAA as Anti-Aliasing and can be very good in most scenarios.