No not really, like yeah it's good to have a 5-star island for the lily of the valleys but I won't go out of my way to have a 5-star island just for that, I mean it'll just be 5-star eventually anyways once you're progressing with your island...
It's possible to progress your island beyond 5 stars, though.
My island is supposed to be a forest with clearings for various things...but mostly a forest.
As soon as I added shrubs as well as trees...I was back down to 4 stars.
It looks loads better for the look I'm going for though, so I can live with that.