They have had a lot of different writers - 22 listed on the IMDB. I suppose that lines up with the changes in Cassie's character and the atmosphere of the show.
From a mysterious witch with a black cat named Isis and a witch's broom, who dressed in black, was truly magical, and had an occult shop (Bell, Book, and Candle - remember where that name comes from?) to a woman who dresses "normally" and whose shop has been completely transformed into a light, bright gift shop that no longer dispenses potions and oddities, the concept of a Good Witch has been consistently watered down. Now it is pretty much just a romance show, for Cassie and all the other characters. It is a pleasant show, just not what it originally was.
In short, Cassandra Nightingale, the Good Witch, has been Hallmarked.