Phuket isnt unspoilt.
Its a tourist island.
And hotels are plenty.
Would you need a 5 star hotel if you are going to be roaming the
islands all day? Your luggage need the 5 star hotel?
For shopping, go Bangkok.
For Spas, go Bali.
For Scuba, go only if you got the Open Water Padi Licence & go
with yoru dive group.
For eco tours, ridng elephants on mainland will be good
enough.
For exploring the islands. Unless you really can canoe. Your arms
has to be strong.
For the food, unless you got a local there, with at least a vehicle
to bring you to the eat all you can local buffet for 100 baht. And
you can eat all you can the seafoods, thai style & drink those
cheaper then Singapore Whisky & Beers.
Or you are daring enough and rent a small kup kia and ride around
to the temples and explore the island. its roughly the size of
Singapore island, without the Woodlands part. And the beaches is
beautiful...if you manage to find them.
Otherwise, stick near to your hotel and brings a good book and a
sunscreen to laze at the beach nearby.