Increased density = more transistors. Don't be pedantic.
You can massively parallelize rendering a movie in advance because you can do each frame on its own CPU. Rendering in real-time is much less easy to extract this kind of parallelism from, particularly if you have hard real time constraints.
If we can make higher pressure capable small pipes we could run then all faster. I bet there's billions being invested in solving this problem, but that doesn't mean it's solvable.