Why is computer network so complicated?

This goes for ANY field of endeavor (medical, legal, engineering, etc.) That is just the way it is, doesn't mean you or someone else is "stupid", only that their aptitude is more geared to a different area of study. Best advice I can offer is if you TRULY desire network certification, keep studying everything you can find. Perhaps find a local IT person with similar credentials that you desire and ask questions, inquire about part-time work like apprenticeship/internship with them, or maybe even tutoring you, giving you a hands-on experience sometimes makes graphs and text come alive.
Good luck!
Wiz