Stop putting vignette-like filters on top of everything... or any filters in general.
They'll make any image terribly flat.
Regarding the first sig:
The render has too much contrast, the vignete (as said before) kills depth... and there's too much mist.
Regarding the second sig:
The "malevolent" text is utterly horrible, the second text has way too much contrast and its shadow kills depth too.
The render's added grey color is really bad, it isn't even blurred properly on the left side.
Lastly, the cuts. Any possible glance of depth has been immediatly smashed by those damned cuts! (Along with the vignette).
Tips to improve:
1) Keep it simple, don't over-do it. When your brain says "i finished my work, let's add some filters" pick your nearest frying pan and pretend to hit yourself, those negative thoughts will leave your body soon.
2) Play with your render: at the moment you just place the render, add a background, some text, random filters and call it a day.
What you should do is place your render and add stuff around it, on top too.
3) Play with layer types. At times you can just pick a random color, smash some of it around the image, turn opacity to 70% or so and check what the different layer kinds do.
Early on it's helpful to notice "possible cool things you can do". ;D