No. Mainstream literature usually aims to reach a wide audience including all ages and sensitivities. Dirty sex fantasy stories are often considered inappropriate as they contain explicit sexual content which goes against the moral and ethical standards of the general public.
No, it is not appropriate. Such stories are very private and should be kept between the couple in an appropriate and consensual context. Sharing them freely in public or with others violates the privacy and propriety of the relationship.
Read a lot of non - sexual literature to get a sense of appropriate content. When you do write, constantly ask yourself if your story could be misinterpreted as having sexual undertones. If there's any doubt, rephrase or remove that part. Also, consider your target audience. If it's a general or young audience, you definitely want to stay away from anything that could be construed as a dirty sex fantasy.
In modern literature, the presence of dirty sex stories is a controversial topic. On one hand, some may argue that they are inappropriate as they can be seen as vulgar and violate moral and ethical norms. However, others might say that if they are used in a context to explore complex human relationships, sexuality in a psychological or sociological sense, they could have some merit, but they should be presented with great caution and within certain boundaries.
In a civilized society, we should uphold good moral and ethical standards. These types of stories are not in line with the values that a healthy society tries to promote, such as respect, equality and propriety.
There are many other interesting and positive story genres like adventure stories or heart - warming friendship stories that are much more worthy of our attention.