The above should be taken as an evocative analogy for the complexity and senselessness - don't go too far trying to apply your intuition about designed/engineer

The above should be taken as an evocative analogy for the complexity and senselessness - don't go too far trying to apply your intuition about designed/engineered systems (even really bad fragile ones) to biology. The reason it's so crazy is that it's been evolving for billons of years - random mutations without one discernable iota of forethought or intention. The reason it works at all is that we're looking at the tiny fraction of accumulated changes that didn't die out. Evolution by natural selection builds crazy awesome, intricate things - just not sensibly engineered ones.