Bad Performance on RTX 5090

I have a rather high end PC. RTX 5090, i7 14700KF, and 32GB DDR5 RAM. Every setting maxed out at 4K, even with DLSS set to performance, I only get around 120FPS. CPU usage around 45%. GPU usage around 50%. GPU undervolted using MSI Afterburner for stock performance at lower voltage / wattage. Even when using DLAA I still get around 120FPS. Every other game I play runs well above this and often reach or exceed my monitor's max refresh rate of 240HZ. Marathon should not be running this poorly on my PC.