How can we increase the resource’s popularity?

Yes, and most importantly, there should be fewer posts with such content.
For example, a person comes from a resource that has shut down (not necessarily Dungeon, it could be another one), wants to play, looks at the topics, and sees such posts. They get scared and leave. It's immediately clear that they are not welcome here.
And the question of who to consider "one of our own" and who not is also debatable. If a person came here from another resource but has organized about ten tournaments here, and shown dozens of people a site like World of Xeen, isn't he more "one of our own" than some loudmouth who has played twenty online games here and considers himself a defender of the resource?
Xenophobia has never led to anything good.