This colorful planting scheme uses an unusually large variety of plants. Most gardens don't use such a large combination of perennial and annual flowers. Combined with the evergreens and ornamental grasses, it has a tendancy to appear too busy and cluttered. And with every inch of space planted, the only access to the stream or pond is the visual appeal from the stone bridge.
While it looks very full and somewhat appealing, there is no balance, consistency, or unity in the landscape that you would get from repeating some of the same variety of plants throughout the garden. It's still possible to have a full and lush garden stream landscape by using a smaller variety of plants that accent the rocks and bridge and leaving some free space.