I think complexity should be seen in proportion to the challenge at the time. Yes, the main feat has been repeated - later. For their time, the Voyager probes are state of the art devices, and their design has clearly proven durable and forward-thinking. (Not an entirely empty opinion, either - a couple of months ago I went on a bender and read journal write-ups of bugs they fixed over time, etc.)

Sure, with this line of thinking perhaps you'd have to compare them more with the Pyramids or Antikythera-type devices, and I think I'd be comfortable with that.