Like anime, everybody's overdressed and has too many unique quirks. Think of Scooby Doo, everybody's in plain clothes, except maybe Fred's ascot. Now think of Kingdom Hearts, everybody's in fucking BDSM gear covered in belts and straps and studs and zippers and spiky hair.
Very busy design, while not necessarily "tumblr", is amateurish design. Even when you WANT busy design (webm related) you have to be very picky about where to be busy and where to be clear and simple.