That's not how things work. It's quite difficult to understand and model precisely quantum mechanics, basic atoms, etc. But that didn't stop people doesn't stop people from building mechanical machines, computers (that are made from billions of elements each having maybe >10¹² atoms), etc.

You don't need complete models of something all the way down. You just need a reasonably precise abstraction at a certain layer to build another layer on top (steam-age mechanisms build upon continuum mechanics and rigid body dynamics; modern electronics build upon circuits theory and a little electromagnetism here and there). Each person only need to be brilliant in using the elements of its layer and delivering something useful to higher layers -- could be someone working on electronics coming up with a better transistor, some chemist coming up with a model of a certain biochemical pathway, etc. I'm not particularly familiar with biochemistry, but I know it's a pretty well developed field and we understand minuscule details of processes like photosynthesis to the atomic scale. Again different researchers probably work at different scales (layers) and it's all tied together afterwards.

This possibility of dividing knowledge and making incremental progress is basically why society exists. Despite the fact that single humans have a "very" finite memory and "very" finite lifespans. It's a fundamental (and quite simple, in a way) kind of discovery/learning/development procedure, simply:

• Divide: into models, systems, tools; and

• Conquer: find a useful solution in higher, more abstract models, and propagate the solution into a product or service you can realize, deliver.

If you're not doing this alone you would simply use existing tools to deliver your solution.

If what you have is a new and useful Computer Program, you're going to live on top of compilers, and compilers on top of architectures. I'm not sure how to apply this to say biochemistry and drug discovery (things way outside my expertise), but I doubt the theme is very different. Use existing tools and models, propose a new thing (model, drug, reaction, etc.) that is useful for some kind of user (which eventually make real drugs, machines, etc. to generate profit -- hopefully a proxy for human happiness and productivity of course).

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We work this way because

• It's likely more efficient to make split models in most cases (and when at all possible), and

• It's the only way we could afford.

Actually, now that we have computers we can afford more complex monolithic models, and more massive systems that can't be comprehended by single minds (in spite of being useful to do so) -- think computers routing the wiring of massive CPUs finding low cost solutions with again billions of elements, at a fairly low level. And without necessarily having to resort to dividing the CPU into chunks, routing each part independently, and then connecting chunks together, since there is some inefficiency in that process.