Hmmm lets see
1. iRacing is not even doing close to what rFactor 2 is with regards to lighting
2. rFactor 2 has moving clouds which make a difference to how the lighting shines, and clouds being calculated aswell
3. rFactor 2 has full 24 hr realtime , which affects the sun in game, clouds, lighting, etc and its all calculated in real time
4. rFactor 2 has fully calculated rubber and grip build up graphically and in the physics
5. rFactor 2s rubber and grip build up is all being calculated in real time where ever every single car on track drives/doesnt drive over
6. rFactor 2 has the rubber/grip build up also working in a "drying the track/line" when its wet, its also not pre determined but happening in realtime depending on where every single car including every single a.i. car drives over
7. Probably a bunch of other things I didnt mention
So ya if people can actually think about it ya it doesnt suprise me rFactor 2 is much slower than iRacing, its doing so much more underneath, plus on top of this all as everyone knows its still not optimized and in beta.
Man I remember there were fps improvements for rFactor 1 even after release, let alone while the game was still in beta months before release.
Still, I don't think the performance hit should be that severe to people with high end cards. Besides, half of the list you mentioned are rather up to the CPU, not the GPU. We know we are still in beta, and there obviously are optimizations to do, so I still don't see performance as a serious isse (although I do think people must manifest about it). The graphics engine, yes.
Rodrigo