Well, I am just talking about this composition. The trees look quite realistic to me. The island without the trees looks quite believable to me too. The clash I feel is to combine these two items into a single composition.Many, if not most bonsai are not.
In general: I would prefer trees for their natural beauty rather then for their growers ambitions to astonish viewers. Trees that have a believable story to tell. Mr Kunio Kobayashi has a great video about the difference doing bonsai for money ( what he has done quite successfully for most of his life ) or for their natural beauty / character ( where he feels to be now at the autumn of his days...