Connotations are very effective to writing because they make words have more emotion and feeling. Negative connotations make words seem, negative, like an insult. A positive connotation makes a word positive, like a compliment. A neutral connotation doesn't have any emotion of feeling to it.
For example,
Negative connotation:
The shirt's price is cheap. (this would have more of a negative feeling because it is implying that the shirt is bad)
Neutral connotation:
The shirt's price is affordable. (This doesn't have any feelings or emotion.)
Positive connotation:
The shirt's price is a steal. (This has more of a positive feeling, almost as if the person is excited to buy the shirt.)
Connotations also have different intensity, for example:
Good, Satisfying, Awesome, Unbelievable. This order is from low to high intensity. Each word getting stronger and stronger.
Connotations bring more depth to the author's way of writing, especially in critiques.