Fine, allow me to find CPU bound games with a 4090 using a 9800X3D. I cannot show that the same CPU with a lesser GPU would have similar performance because nobody tests that way. Here are some charts that show a 9800X3D pulling massively ahead compared to a 9600x which logically means a lesser GPU than a 4090 can be paired with the 9800X3D to get the same or better FPS as a 9600X and a 4090.
Theoretically you could get a GPU that is X percent slower than the 4090 + 9600x where X is the amount the 9800X3D is the percentage faster than the 9600x and pair it with the 9800X3D.
Sources for the below images here. There are tons of games that are not commonly benchmarked that would also support my argument. MSFS was not benchmarked hear, nor any of the games from the genres I mentioned above in the entire 9800X3D review from TPU. Below are stock for stock comparisons.
Baldurs gate 3 The 9800X3D performs 51.9% faster than the 9600x at 1080p
Cyberpunk 2077 The 9800X3D performs 21.5% faster than the 9600x at 1080p
Elden ring The 9800X3D performs 28.0% faster than the 9600x at 1080p
Remnant 2 The 9800X3D performs 21.2% faster than the 9600x at 1080p
Spider-Man Remastered The 9800X3D performs 25.5% faster than the 9600x at 1080p