That's because GW1 was a quality game; what was discussed on the forums actually mattered (at least stuff like tactics, builds, how to do things). GW2 doesn't have that. It would be like having an in-depth, two-year discussion about Resident Evil 5 even though that game can be summed up as "play it like Gears of War". It is difficult to make a build in GW2 that is so bad that it actually matters; in GW1 it was the default. In GW1 PvP, skill would make a huge difference, to the degree that it allowed teams to win even if three players were missing etc., in GW2 skill matters, but not nearly as much because the game does not offer the complexity that would cause skilled play to become a leverage.
GWGuru still had plenty to discuss after two years.
There's simply nothing to talk about.
GW2 is not dead however. Player count has been dropping for a long time, but if you log in and play, you see people, at least in some areas.