Are jehovahs witnesses gods spirit directed organization?

if so then why are the teachings always changing? if they were directed by holy spirit would it not seem logical that the direction would be acurate, easy to understand and there would be know need for the light to keep getting brighter. so that when taught to the congregation once it would not have to be changed later. most recently the generation o f 1914 once taught that this generation would see the end of this system now a totally different concept is being taught.there have been other changes as well once taught that 144,000 would finish earthly course before armageddon now not all would be in heaven before system ends.several other changes as well. the bible has not changed since it was written by spirit direction why all these changes?one only has to read the comments in this forum to see the reproach this type of confusion has brought on GOD'S name.