The "blurring" might also come from the shadows, but the texture still lacks something

I agree that texture looks like a simple tiled texture applied
with some modifications on some parts.
It lacks details variations and some depth !

But for the price the pack is complete and cheap and like it have been said :

Can you people tell me what's so difficult in makin your own dirt overlay for the existing textures. Hey, the thing is completly mapped, so you only have to power up your photoshop or whatever and modify it.

I agree with that indeed, we can use a paint program and modify
all ourselves make your own normal map or baked normal map etc ...