It's important to read the type of writing you want to write. So, if you want to write short online articles, read lots of short online articles. If you want to write a novel, read novels. If you only read novels but want to write online articles, this will be a mismatch because your articles might end up written more like novels. The same is true if you want to write a novel but ony read online articles.

The great thing about Medium is you get exposed to such a wide range of topics and writing abilities. This is important because it's helpful to be able to notice bad writing when you see it.