Blizzard has released a fresh update (1.3.5) for Diablo 4, which introduced official ray tracing support to the game. With this feature enabled, shadows and reflections should now appear more realistic.
Features of the 1.3.5 update:
Support for ray tracing and improved Ambient Occlusion and Contact Shadows functions;
Fixed some bugs;
Increased stability and performance.
The developers also revealed the minimum system requirements needed for ray tracing in Diablo 4:
OS: Windows 10 (version 1909 or newer);
Processor: Intel Core i7-8700K or AMD Ryzen 7 2700X;