Blizzard has said those addons are not entirely accurate in the past.
Regardless of what they said. Anyone can log into the game, at least in North America, and see it virtually empty. Outside of servers like Tich, Illidan, Kil'jaiden and one or two others, it really is empty compared to WOTLK.
Then again, it's not really World of Warcraft anymore. It's World of Menu's. Everything is Menu based now, everything. There is no social interaction in the game, there is no need to explore the world anymore. You sit around, and use menu's to get into content with strangers. You can literally line up the first drop in subscribers to the exact same quarter they released the LFG tool. Since then, they have only added more menu's.
I just dropped by subscription two days ago. My server is top 10 in PVE progression, top 10 with arena ratings, and according to the server info, top 10 in population. There are no Horde, none at all, and Alliance it self feels just dead. Most other people I know who play, if they don't play on one of the big 5, feel the exact same way.