Thank you for sharing your feedback! If the grain bothers you, there are plenty of settings available that you can adjust to your liking, including the option to disable grain and lens flares if you don't like them. Unfortunately, I'm not sure what you mean regarding the rain hitting the glass.
The Witcher 3 Next-Gen looks stunning, yes, but I am still more of a beginner developer and cannot compare myself to the expertise of CD Projekt RED. They are a huge inspiration and authority for me though.
I can also mention that creating good lighting in a dynamic world with various weather effects, dynamic clouds, and different times of day is a very challenging task. Additionally, accommodating different graphics settings where the lighting needs to look good across all of them adds another layer of complexity. I will keep trying and learning, that's for sure.