Tulik
The Lone Athgari
While I believe opinion plays a big factor in this topic, and personal preference should be considered when coming into a roleplay centered on mature themes, it is also my opinion that you can go overboard with the doom and gloom. I think that if you center on a story and world that is wholly darkness and mature themes you might have an issue. Not saying you can’t have fun in a world like that, but in my personal opinion I think that a world that centered on one thing, especially when it comes to darker themes will stagnate fairly quickly due to the lack of diversity when it comes to experiences and plot points, with the only change being brought about by “shock factors” that have to grow more and more grotesque to one up the last because there is no real change in the scenery of the world or story.