I could be overthinking (probably am), but this quote by Asagiri made me think that the series is VERY reflective of their audience, meaning that these characters were made THINKING about the audience, and everything in the series- things like mental health portrayal, representation, etc, were all made while considering the audience (since he emphasizes his audience in this quote a lot).
--> What Asagiri said at an interview
So I have a theory- ish thing about the title of the series: Bungo Stray Dogs! Let me first lay out my interpretation of Asagiri's quotes build it up a bit...
I think this is one of those events where, unless you've directly felt it or gone through it, you can't actually grasp it that well, but some people find their own lives to be dull. Maybe it's something related to depression, but when you come to that point, you don't feel any attachment to your life, and you don't find any reason to engage in your life fully. It's kinda like existentialism, but worse, because instead of finding joy and acceptance in the lack of meaning in life, all you feel is hollow, and all you're left with is a desire for escape.
And for these people, it's these times when stories are needed. When Asagiri mentions that this story is not for certain people, he means that BSD is not for people who are comfortable in their lives. He means that BSD isn't a story too needed for those who don't mind being fully engaged with their lives and are generally satisfied with being alive. Of course, they might have their own problems, and by "them" I don't mean people who are 1000% satisfied with their lives, but unless you feel utterly devoid of meaning in your life, fiction is still an entertainment and a hobby to pass the time.
On the other hand, some people (as aforementioned) actually do require stories to not just "live", but genuinely to survive. They require stories "like oxygen" because these are the people who replace their lives with stories like BSD. It's for people who cannot find their own meaning in life and therefore depend on stories. Without it, their lives start to lack joy, and with a life you do not enjoy/care for, it is impossible to survive. So to live on and cope with the weight of their lives they cannot handle, these people heavily depend on fiction. Since they literally depend on fiction to live, they are likely the people "that aren't good at living" that Asagiri is referring to. It's possible for Asagiri to have said this, hoping that these people are the ones he is helping through his story.
We, as people outside fiction, are able to look inside fiction, see people with the same problems as us, and watch as they move forward DESPITE their struggles. So when in real life, we feel stuck, we're able to gain hope from seeing these characters heal from their traumas / overcome challenges. This therefore, is probably the effect Asagiri wanted to have through his writing. He probably wanted to help those who depend on fiction by: 1) providing them a fiction to bury themselves in, but also 2) making (mentally) relatable characters to help the audience (aka the ones not good at living) survive through hard times by getting hope). Perhaps this is why he said his book could "be the oxygen" for these people. He wanted to offer both immersion and restoration.
Now to the theory!! I think this is also why the title is "Bungo Stray Dogs". 'Bungo' means collections of Japanese literature/texts, and stray dogs are, well, dogs who wander around the streets. Bungo (literature, etc.) is fiction, and stray dogs are us ("lost people", as said by Dazai). In translation, therefore, WE are the stray dogs, lost in fiction. Since Asagiri mentions right off the bat that he canceled out "people good at living" as his audience right from the start, I think this could have influenced the title for this series being "Bungo Stray Dogs"- representing those who are wandering in fiction, looking for a purpose in life beyond merely surviving.
