Ubisoft reveals Assassin's Creed Shadows PC requirements – and just as I thought, you're safe with your RTX 4000 series GPU
If the RTX 4090 couldn't run Shadows at those settings and maintain a good frame rate, there would be reasons to worry about the game - but as some of the other requirements reveal, an RTX 4070 Ti Super will reportedly be enough for standard ray-tracing and achieve 60fps at 4K,