This is not how it (supposed to) work. When an employee leaves, they are supposed to show the ropes to their replacement. And if they don't, the person hired into their position is expected to learn it anyways (it will just take longer). So, the knowledge about the product is preserved.
If your company is so unique that it simply... throws away the knowledge and just keeps the physical artifact produced by the now missing employee... that just sounds like an awful way to run a business. Maybe cheap, but awfully dangerous.
> However, we have an on-demand ability to get an arbitrary level of understanding quickly
You still seem to not understand the problem. The production outpaces understanding. The "quickly" you are talking about here is no more. For every thing you understand, two new not-yet-understood things appear. The speed of understanding is what's important, not the theoretical ability to understand, given infinite time.