If it's not a lens you need, then don't keep it, but exposure has nothing to do with the lens. Do you know how to use exposure lock? You see that pic with the brick buildings and the white sky? Meter off the sky, lock the exposure, and then shoot the same pic. Now the bricks will look under exposed and the sky will look nice.
The issue is the wide range of brightness in those pics. The bricks are in shadow, the sky fully lit. The Washington statue looks better because it's out in the middle of the field in full daylight, so it's much closer in brightness to the rest of the surroundings.
Generally, a lens will not impact metering. Color, yes. Metering, no. Try shooting the same pics with your 18-55IS kit (if you got that with the camera), and you'll see the same results.
The only other issue is with a SWA, you maybe be getting in a broader scene, and more likely hood of both exaggerated shadows and brightness. Try metering off the sky next time, then either use the M mode to manual put in the f/stop and ss, or exposure lock.