It does always sound really crazy because in our minds 3D is more complex than 2D, but in reality 3D printing is actually really really simple, it's basically just 3 motors, a heat block, and an extruder, that's pretty much it.
Whereas 2D (inkjet) printing has all of the above (minus one motor), and actually comes with a few non-trivial non-printing related expectations as well, like loading and expelling a print surface (often many in one print), optionally flipping said print surface (and this requires that ink has dried as well) and colour processing to map computer colours to real-world colours.
It's actually even more complicated than that. Modern printers include a raster image processor (RIP) [1]. This specialized software converts vector graphics, text, and pixel-based images into a raster dot pattern that controls the print head. The individual dots that get printed can't be varied in size or brightness, so the variations in image tone are controlled by the density of the dots in the raster pattern. This is called halftone [2].
Whereas 2D (inkjet) printing has all of the above (minus one motor), and actually comes with a few non-trivial non-printing related expectations as well, like loading and expelling a print surface (often many in one print), optionally flipping said print surface (and this requires that ink has dried as well) and colour processing to map computer colours to real-world colours.