Let’s be honest, when they made Cataclysm, Blizzard made a huge mistake. Numbers speak their own language. The number of subscribers went upward from 2005 to 2010. Topped in 2010 and then came Cataclysm, and the numbers when down. A bit up right after Mists of Pandaria was released and since down again. We are soon down to the level we were in 2006.
See the chart here, from Statista: