Islands have a unique culture associated with them. Access may be limited and often supplies are shipped - or flown -in.
For the purposes of RetiredTraveling.com context I'm defining an "island" as a destination that one would go; either by air or boat. .... While maybe no Mai Tais, I Included Iceland here... Tasmania also (amazing place).
Technically, New Zealand is an island nation with 2 major Islands (North & South to avoid confusion).... Manhattan is an Island... NOT included here! Austrailia is also an Island - albeit a huge one! Also NOT included!