While I agree with you, I think it's important not to overgeneralize today's methods of 3d printing with being the only methods possible.
For example, I've often speculated a lot about the prospect of using thermal spraying as a printing method. That is, you have any sort of powder or other fine material, fed into a chamber with the Venturi effect. Therein a custom mix of air and fuel is injected at specifically chosen partial pressures. Consequently, depending on what material you're using, you can choose the impact speed and temperature of the particles, anywhere from "cold" to thousands of degrees and anywhere from less than 1 meter per second up to a thousand or more. The size of the nozzle determines flow rate, so you could swap between different print heads for bulk vs. fine detail. You're essentially unlimited in what materials you can use. You could, for example, print isotropic fiberglass composites by alternately spraying fine chopped fibers and a resin. You could even do so by spraying simple quartz sand at high enough temperatures, fast moving molten sand in the air forms fiberglass. Your resin could be a thermoset powder heated during travel, an epoxy that reacts after being mixed on impact, or a wide variety of other possibilities. High velocity spraying of metal powders produces metal structures stronger than simple casting. You could spray at low velocity chemicals for the filling of things like capacitors or resistors. Thermal spraying is often as it stands used to apply durable clear coatings to materials to protect them, so clearly transparency is no problem. And any printer built around the principle of launching varied small particles at high speeds could polish, sandblast, coat, engrave, paint, or do whatever other surface treatments you wanted. It could build scaffoldings and then obliterate them afterwards. And on and on down the line.
It still wouldn't let you do fine detail, though (if anything you'd struggle to get as high detail as with conventional 3d printers). For detail work you'd have to add in a lithography setup. Some types of feed inputs would require refrigeration to remain as dusts. And of course some things would still be easiest assembled with literal assembly, aka, a robotic arm or two would be quite useful. So we're getting more and more complicated here.
Do I think such a thing is right around the corner? Of course not. Could my conception turn out to not work well at all as a 3d printer? Quite possibly - as far as I know, nobody's ever tried. But I'm just pointing out, when talking about future tech, you shouldn't evaluate it based on how today's tech works.