You are having a hard time making any model that looks good rendered. You had the best luck with a blender metallic texture with a random rusty aircraft carrier image. You had a dream of not having to do custom textures — of modeling so big parts could just be metal and details would be separate polygons matched to some greeble texture. Have not found success there.
Maybe your base texture is not good. Should you be able to make a cube that looks like a real metal object hanging in space? What’s the secret to that?
PBR = “Physically Based Rendering”. “A PBR texture is just a set of images for albedo, metal/specular, roughness, normal, displacement, ao, emission, to feed to a PBR shader.”
https://polyhaven.com/textures/
Adobe Substance is the de facto standard tool for texturing and other fanciness. Non-subscription version can be purchased on Steam for $200.