Product recognition and marketing becomes more difficult if the appearance can change dramatically. And Aqua is very recognizable. Photo Realistic Icons Icons can be as large as 128 by 128 pixels with 32-bit color and an alpha channel. I know I have missed the trash many times. Large icons are a bonus for many and may be turned off for users who do not appreciate them.
Simplicity is still a key component of icon design.
The user interface may scale a large icon down to 32 by 32. Complex icons may become illegible when scaled. Translucency Menus Menus are translucent. I cannot find a single benefit to counter the distraction. When a window is minimized the entire window is transformed and shrunk in similar fashion to the smoke in the proverbial genie bottle.