How can we increase the resource’s popularity?

The main thing is that outsiders don't write inappropriate things here, and everything will be fine...

Yes, and most importantly, there should be fewer posts with such content.
For example, a person comes from a resource that has failed (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 us" and who not is also debatable. If a person came here from another resource but has organized about ten tournaments, shown the World website to several dozen people, isn't he more "one of us" 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.