Omar’s right, I forgot about all those heavy procedural textures.
One thing that you can do is reduce the Detail in all the Noise Textures until you start seeing too much difference; usually a level of 3 or 4 is enough and above that the differences get really small, but the calculations go sky high, The Detail levels grow exponentially, while the visual differences get less, each time you ‘level up’. It’s one of those ‘secret’ tricks to save resources, while hardly reducing visual quality.
Also, Mixing everything before a Principled Shader is better (calculation-wise), than using a Mix Shader after two or more Principled BSDFs.
