Yes, they can be okay. When well - written, sex scenes can add depth and authenticity to a story. For example, in some classic novels, they are used to depict the passion between characters in a way that reflects the overall themes of the book. But of course, it should be done with taste and not just for the sake of shock value.
Yes, there are some relatively intimate scenes in 'Marriage Story', but they are not overly explicit or gratuitous. These scenes are used to convey the complex relationship between the characters in the context of their marriage.
It depends. In some novels, sex scenes can be an important part of the story if they contribute to character development or the plot. But in others, they might seem gratuitous and unnecessary.
I'm not sure which specific 'less the novel' you are referring to. Different novels handle sexual scenes in various ways. Some may use them to explore complex relationships, while others might use them more gratuitously. Without knowing the exact work, it's difficult to analyze in detail.