I think the issue is whether there is a reliable way to determine what the Bible is saying on these topics. If a person is convinced that the JW governing body (or the Pope, or any similar recognized leadership) is guided by the holy spirit, then whatever they choose as an interpretation is what god wants. But how to determine which of those (if any) is being guided by god?
There are debates going on in this forum right now about Christian teachings, and the people involved seem very smart and well-informed and also sincere about what they believe. But there is no consensus. If bright, honest, and devout people cannot come to an understanding on issues as important to them as the trinity, how can we ever determine who is being guided by god today?