There's nothing wrong in your screenshot.
It's not entirely clear if you don't like the fact those lines are too white, too tick, or both. Colors are of course highly subjective, but we can always do tweaks if enough users said they don't like something.
About being too tick, we are a bit limited by the choice of a non extremely high resolution textures for the background, considering the large airport size, in order to save the highest possible amount of texture memory that could be used for the actual main modeling. it's not as the scenery has "low res", because it uses 4 4096x4096 textures but, considering its extension, the pixel/meter ratio is not as high as other sceneries we made in the past, but this was a choice driven by the fact that, a PBR scenery consumes from VRAM than a regular scenery, so we had to save something.
This means it's not easy to create "thin" lines on the underlying background. Of course, most of the ground textures are very high resolution, because they are made using a different method, you only get a lower res on those spots not covered by aprons.