If FSX won't run above 12fps on your rig or any other, and you want to keep throwing cubic money at it, by all means, go right ahead. I'm happy for you.
Depending 'where you are' you can get 60 or 70 fps but if you're within a detailed airport [where you can recognize car makes and models...the detail is that fine] mapping square kms of topography in real time...and AI flight paths as well as your own ...GPS...radar....animations...specular shine...self-shading....and when you see them the stars are in the right places.... realtime weather from real weather.....all in a long-in-the-tooth proggy being replaced by MS with a 'toy' version that's more 'game' than sim.
The skinning for the aircraft is significantly more complex than a GUI as it seems just about every model does it differently...and the only saving grace is much of the bigger stuff uses DTX5 compression otherwise the image files are huge.
The rest of the world uses it because it is the best flight simulator available, and yes, it's the software....it cannot be made 'properly' multi-processor aware and still hits ram limits [not 64bit].... and it comes from an era when GPUs were considerably weaker than those available today.
NOTHING can genuinely run it maxed out...everything is a compromise....