Gamma/Tone Washing Out Image - How to Fix?

I have a city in a generic forward renderer with simple lighting: blue-ish ambient, a cubemap for some additional lighting, and a directional light for the sun. The scene looks fantastic.

I have the same scene setup in Unreal Engine. I tried using a solid sky light color and also a cubemap for sky light. I used these with a warm direct light representing the sun. I was highly disappointed with how washed out the color was and after a while I became convinced it has something to do with either the gamma correction in one of the core shaders OR it’s a flaw in how the lighting is blended with the sample diffuse. I don’t know exactly which. I tried completely commenting out the gamma correction step in GammaCorrection.usf and reloading the engine. It made no difference in the image. Can someone please tell me what’s going on that’s causing Unreal to compress and wash out the colors and how to fix it?

Below are two images. The first more vibrant and richer one is the generic forward renderer. This is the look I want.

The second image is the Unreal render. Note how flat the relative colors are.

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