And we could get a sound engine connected to engine physics like in Richard burns rally and old (up to v1.03) netkar pro, and we could get the amazing complex environmental sound physics of battlefield, and we could get the awesome online portal/community that iracing has. In the end we will have the most perfect game of all time

.
Unfortunately we have no idea just how much resources the core physics, graphics and overall game engine need, we are not coders or software engineers, and even if we were, we have no access to the core game, physics and graphics engine's deep coding and construction of it, we just have modding tools, so we really have no idea whats going on behind the scenes of the software.
Maybe the graphics engine is still too much based on a very dated (late 90's early 2000s) core foundation (despite updates) which limits what it can do? Or maybe it can do it all but is very in-efficient at doing it because of it's dated foundations? Or maybe the physics/tyre core engine is very very resource heavy and makes it very difficult to have great graphics at the same time without blowing up our computers lol? Or this, or that, etc.
Who knows.
If the answer was simple, then you could get 100 first person shooter games and say to all of them, "why don't you all have the graphics of crysis??!"
If the answer was simple, you could get every first person shooter game out there and say to them all, "why don't you all have the sound engine like battlefield??"
If the answer was simple, you could get every sim out there and say "why don't you all have sounds connected to physics like rbr".
Etc etc etc etc