The fact is 1914 and the adjoined "This Generation" doctrine was a failure (false) that was taught and preached by the JWS throughout most of the 20th century.
The new overlapping generation doctrine was established to put a band aid on the 1914 doctrine.
The WTS leaders are careful to not openly disregard and admonish doctrines that were previously made for in doing so it weakens the proclamation that their bible interpretations are accurate and "The Truth" .
Nevertheless the 1914 doctrine as well other doctrines such as 1975 were indeed successful in enhancing the literature the WTS sold and proliferated.