The first patent (which had no attempt to commercialize) was in 1979. Most early research, with largely failed attempts to come up with a commercially viable product, were in the mid 1980s. The tech has slowly advanced since then, and nowadays is becoming rather mature.
I don't know why this is seen as a way to diss 3d printing. Some people's hatred of makerbots and their ilk is so great that they can't accept that 3d printing broadly has developed into actually useful production processes in some fields. Rocketry is a great example. It's just silly to have to make (and warehouse) moulds or stamps for parts that you only need a couple dozen of and which you may revise after just a couple launches. Now that 3d printing technologies have advanced enough to produce high quality metal parts, it's properly taking of. It even pairs nicely with CNC, there's now hybrid 3d printing / CNC machines out there. CNC gets you the coarse, primary shape and 3d printing adds in the intricate and/or jutting out components.
3d printing is a very useful technology for low volume or rapidly evolving part runs. No need to play it down just because Makerbots exist.