I used this texture: https://www.poliigon.com/texture/metal-spotty-discoloration-001 used the color map and then the displacement map, which I hooked up to bump node and then to normal And this is what the displacement looks like [it's isolated with the node wrangler, to show what I mena]. The edges are blocky and jagged. Why is it so ugly? I tried Changing linear to cubic and other options. I know the color space should be non-color data, but that doesn't change anything for me. I know I can lower the bump height but that's just about it - It lowers the height but the blockyness is still there
Your displacement map does not have enough information to create a smooth result. You should be using images in 16 bit per channel (or higher) and not crappy jpgs (8bit per channel compressed).
On top of that you should not use sRGB for either map, but Non-color. sRGB will distort the map information.
Additional info on the following links: