It gave me the opposite impression. During her hallucination at the end of the story, the main character imagines herself telling her daughter that she hated herself because she didn't know how to care about herself. I think the takeaway is the importance of self-worth. The ending is somehow bittersweet (rather than just awful) since the main character finally realizes this in her hallucination, and, in part due to this, her death isn't entirely miserable (though it's largely thanks to her high).
I don't think she just "loved sex", at least not the encounters that take place over the story. When she has sex (and isn't flat-out raped), she is doing it for money, for a hit, or to please her boyfriend, whom she believes she loves and wants to believe loves her, which again seems to be out of lack of self-worth. The artwork implies that drugs play a large role when she has a pleasurable physical reaction in these circumstances. The message seems to be not that anyone shouldn't want or enjoy sex, but that good people may be gradually pressured/coerced into lifestyles with unhealthy sex for bad reasons and out of bad circumstances, which is modern enough.
You might say that it's arguing against plain promiscuity using the main character's awful story as a strawman, but I don't see it that way. The story is set up entirely to have the reader sympathize with her, so by the time you reach the hallucination, you want it to be true. Her ultimate moment of self-awareness is meant to make you acknowledge her as a person with the vain hope of actualization rather than just pity her. It makes you want to believe in second chances and maybe to be more understanding and helpful to those who need them. The salaryman who notices her but walks away seems to call this out.
This was an emotional, mostly depressing read (pg. 216 in particular hits like a truck after everything), and I'll probably stick to some more vanilla porn for a while, but I think there's some real merit to this work. It's as much art as it is hentai in my opinion.