And I'm saying it can. But it depends on more factors than just adding a fan. It's where the fan is placed, it's sp, rpm, cfm in relation to proximity of the heat source, the exhaust itself.
Take a hairdryer and stick it 1 foot from your nose. You will feel the full brunt of that 1500w and your nose will get toasty real quick, same as a case side does from a higher power gpu. Stick a fan 90° perpendicular to the hairdryer, you don't get the full brunt of that heat, might not get any at all, or a lot, but not 100%. That's the purpose of airflow, directing, channeling heat. You can have a bunch of fans blowing into a case willy-nilly, that's trapping the heat inside, creating circulatory patterns, or half that many fans placed right will channel the flow into a solid stream in/out.
For the gpu, there's little to no actual flow in that area, it's a hot spot. So you'll need to create flow. Pull as much of that heat upwards as possible instead of allowing it to go sideways into the case side. The case will still get warm, that's unavoidable, unless you stick a fan blowing upwards, perpendicular to the gpu exhaust, but you can mitigate just how much heat hits the side with sufficient draw on exhaust creating a higher low-pressure area, which attracts the warmer gpu exhaust like a magnet.