Getting a five-star island in Animal Crossing: New Horizons is harder than it seems. Achieving the maximum possible island evaluation rating is, of course, a long-term goal; it’s not the kind of thing you can achieve in your first day, week, or even month of playing ACNH. But even beyond that, the requirements for a five-star island are arcane and mysterious. You could build up an island for years, and still be stuck at a four-star rating because you missed some obscure requirement you never would’ve thought of on your own.

https://screenrant.com/animal-crossing-5-star-island-rating-guide/