If you feel like Red Dead Redemption 2 doesn't quite seem as visually impressive as it did before since the new patch, you're not alone. Unconfirmed reports based on screenshot comparisons indicate that patch 1.06 may have removed a lighting effect from the game.

First noted by Twitter user Darealbandicoot, a comparison of the exact same frame from a cutscene before and after the patch indicates a clear difference in how the game renders lighting.
Based on the screenshots, both global lighting and ambient occlusion have been affected. No longer are all objects in the path of the light rays detected making shadows less realistic. Some areas that should be darker have no shadows at all.
However, this is simply the most noticeable change, but not the first. Reddit users have been documenting changes made to graphics and lighting effects since patch 1.03. The game has been subtly changing in its visual capabilities with these patches, and while the point of patching is usually to improve optimization, it seems some downgrades slipped in as well.
Shadows and lighting have consistently been becoming less and less realistic based on the screenshots, and there isn't any clear explanation as to why. The likeliest scenario is that this is a bug that has gone mostly unnoticed until now and that Rockstar has been causing it by accident. Reports are also unclear as to how universal this phenomenon is, and on what platforms it appears on.
Now that the issue is gaining larger traction, it will likely be resolved in upcoming patches. Red Dead Redemption 2 has caused a bit of a ruckus with regards to its graphics before, due to a rather common issue on PS4. This blurring issue resulted in a major uproar and earned an official statement from Rockstar a couple of months ago.
We'll keep an eye on any developments and update you.