Take your parents, for example. Though they may not be able to teach you about business, they do know a lot about life. Though fashions may change, the deeper aspects of life never change. You may be shocked to find out just how much your parents know about the issues you're grappling with right now. Not only do you gain wisdom from questioning your parents, you gain an eternal relationship that you will appreciate now - and for years after they have left this world.
Any human being can make a mistake.
Only God doesn't make mistakes. He promised to take us out of Egypt and He did. He promised to make us an eternal nation and He did. If God says something, it is 100 percent reliable. Part and parcel of Jewish belief is the idea that God entrusted His message to the Sages.