How can I make my landscape materials better looking?

I don’t know why actually. I’m obsessed about creating everything myself. Firstly I want to learn how to create my own assets and I’m excited about it. Secondly, I was thinking using free assets and textures is not sustainable. I’m not sure about this information at all. But In games we played it seems game studios creates their own assets(I’m not sure about that too). I thought they are doing this for reason. But if it’s true I don’t know that reeason too. What do you think?