I hate to burst anyone’s hyperbolic bubbles in this thread, but EVERY airliner designed, certificated and operated throughout the post-WW jet age has been designed by teams of thousands of engineers, physicists and technicians. This is true of Boeings, Airbuses, Lockheeds, Douglases, whatever …
A study-level A350, B787 or whatever is perfectly possible with a team of a dozen or so people given enough time, enough money, and access to enough technical detail to represent the behavior of the systems. The sim doesn’t have to run the same code as the real plane, it just has to LOOK like it does, which is a KEY difference. It’s not magic, it’s resources.