The foundries don't exist yet. It's hard to say what they can do, but much easier to say what they can't - since they don't exist.
Except they - the technology - does exist: the MicroGravity Foundry is a patent pending technology:
And once it makes those parts, you need an assembly line to create the finished product. Which is more infrastructure that has to be put in place. You're basically building an entire industrial base from scratch. It can and will be done, but not cheaply and not soon.
Not really. A human could assemble the finished product in 0g. It would be slower than an assembly line - but you don't need to build Rome in a day.
And if you DO want to build Rome in a day - you will first manufacture the assembly line (assembled by humans) and use it to quickly manufacture the needed products.
^Not even close. What you're reading is the experience of someone who has seen how long it takes for these technologies to come to fruition. Apollo was actually a pretty great achievement and did exactly what it was intended to do.
I've met persons with similar (anger/disappointment/acceptance) outlook vs Apollo:
Some are openly buthurt about the lack of space progress since then;
Some like to think of themselves as wise sages, understanding the difficulties of space development. They come up with what are many times useful criticisms, but they inevitably overreach - 'inventing' problems while obstinately choosing to overlook their obvious solutions;
Some come up with elaborate explanations for why Apollo was, ultimately, a failure - from 'its purpose was flags and footprints from the beginning' to collective psychology/human nature whys.
It's quite probable that, if I look into your posting history, I will find posts along the lines of ~we surround ourselves with past glory (Apollo) in order to look away from the decayed present, like any past, decayed civilization.
Has anybody bothered to ask what would mining these asteroids do to their flightpaths?
Due to mining? No effect.
It's called action and reaction; elementary physics.