I would argue that none of these things are complex systems, in the systems theory sense. A complex system is typically comprised of a network of casual relationships so deeply interconnected that its behaviour is not easily reducible (in the scientific sense of isolating individual behaviours to be examined). Human designs intentionally avoid this and instead strive for mostly linear causality, precisely so we can test and develop individual parts in isolation.

For an example of a complex system (and how unintelligible they are), see this diagram of metabolic pathways in the human body: https://www.sigmaaldrich.com/content/dam/sigma-aldrich/artic...