Theoretically, if you’re adding one atom at a time making a meaningfully thick object requires trillions of layers. Add 1 atom a second across a full layer ~= several years per centimeter of thickness.
Lithography is about as close as we can do, but that takes multiple stages to do each individual layer otherwise you can’t get patterns just undifferentiated layers.
If you don’t need atomic precision for arbitrary patterns there are many options. Crystals can grow much faster, but you have minimal control over how they grow etc.
That was already assuming an unachievable level of parallel behavior and operations per second. Something like 10^15th print heads and feed lines each slapping down 100’s of thousands of atoms per second, is still orders of magnitude to slow to be practical for human scale objects.
Further, that’s the tip of the iceberg in terms of difficulty here. It’s ignoring chemical interactions, thermal issues, sensors, control mechanisms etc etc.
I don't see why this is a theoretical limit. Clearly the existence of crystal growth and similar things show that there is of a much faster speed. Especially with repeating patterns those can be built in parallel and combined. Crystals can grow really fast. If it took so long for atoms to combine and make things then we wouldn't have anything actually made. You can definitely call molecular binding a "trick" when building materials from atomic levels. This is a parallelization method. And we can certainly do trillions of operations a second with atomic level combinations. Just take pure sodium and pure chloride and put them together. Or oxygen and pure iron. These reactions happen down at the "atomic level" and we can do these things at quite a macro level. So I'm just not understanding your argument here.
If the goal was simply to have whatever then you don’t need to do anything, a random rock is perfectly fine. However, if you have specific needs then that creates new limitations. As I pointed out you can grow specific crystal structures faster, but crystals don’t allow for arbitrary structures.
Trying to slap two arbitrary atomic structures together doesn’t automatically work. Sure, you could use some binding agent like glue etc, but now you’re limited to structures which include that binding material. Thus if the goal is to be able to produce arbitrary structures only limited by their stability you can’t necessarily join together separate pieces.
Lithography is about as close as we can do, but that takes multiple stages to do each individual layer otherwise you can’t get patterns just undifferentiated layers.
If you don’t need atomic precision for arbitrary patterns there are many options. Crystals can grow much faster, but you have minimal control over how they grow etc.