It's old but it's not dead. A new expansion was just announced. There are a lot of long time players, so perhaps some of the zones are less active as everyone has their "thing" they want to do, e.g. Farming end game zones, or fractals, or wvw. I have noticed though that the game definitely does encourage a group up and forget behaviour, where you join some group for an evening to get stuff done, then never see them again. Being able to join more than one guild was also a bad game design decision imo. It encourages allegiance to whatever will get your current objective done.