Why do distant mountains appear as pixel blocks while high-speed cruising in Forza Horizon 5?

The pixelated mountains broke my immersion completely. I tried lowering texture quality, but the image became blurry. I used GamePP Shader Compile Queue Manager to clear the 4.5GB cache. HWiNFO showed stable temps at 62-68℃. RTSS confirmed frame times improved from 15-22ms to 8-11ms, restoring visual clarity.