Does Prov 4:18 really justify an organization replacing doctrines and failed prophecies with new doctrines and prophecies, or does it simply contrast the benefit to the "righteous" of obeying a wise father (Prov 4:10-19)? False teachings can be called "false words" and Prov 13:5 says, "A false word is what the righteous hates..." When the WTS changes a teaching to something that is totally different, is it like a light that is getting brighter and brighter or more like having one false light (word) completely turned off and a totally different light turned on? Do you think the WTS would be critical of any other organization that changed its teachings as many times on as many different issues over the last 100 years as the WTS has?
The Watchtower has not changed any doctrines since its inception. Jehovah's Witnesses basically believe and teach the same things as did the original Bible Students. Prophecy, however, is another matter. The topic of "new light" is considered in this article - Is the Light Brighter for Jehovah's Witnesses?