An adaptation should always be analysed, first and foremost, as a standalone piece of media.
Change is an inevitable part of the process of adapting a work, especially if that is to a different medium or is done a significant amount of time after the release of the original. This is not – as the underlying suggestion of a lot of critique implies – an inherent ill. As the effect of a story on its audience never truly ends, arguably neither can it ever be considered complete, for there will always be a multitude of different reactions to and interpretations of it.
With this established, those that are adapting the material need to be held accountable for the messages and implications of the art they create. There is often nothing forcing the adaptors to follow the original work as closely as possible, asides from the belief that they should do. If a depiction that could be considered harmful cannot be easily removed, then there are ways of handling its impact, such as introducing new aspects to the story to counterbalance it, or through reframing the narrative.
It is important to remember that there is no such thing as a perfect piece of fiction, with numerous creators finding that their audience interprets the story differently to how they intended, having included tangents and set pieces from earlier drafts which lack purpose in the finished work, and even disowning the final product entirely.
Concepts such as authorship or auteur theory are useful as analytical lens, however it is important to recognise that all media is to some extent a collaborative process, and therefore does not have a singular, correct meaning.
There is nothing inherently wrong with an adaptation which adapts only certain elements or characters from the original story. This type of work is preferable to one where parts are included out of a sense of obligation, and also has the potential to be insightful, even revelatory.
While books are often loftily referred to as the best way of telling a story, this is largely due to a combination of them being the source material of the majority of adaptations, as well as the status given to particular types of stories and genres. All mediums have their own conventions, formatting, demands and restraints; what may be impactful in one may not be in another.
As vital as interpretation and flexibility are to the process of adaptation, care and consideration needs to be taken when deciding and implementing these changes. These choices do carry their own meaning, particularly when it comes to the framing or prioritisation of certain characters and events, and both can and should be open to criticism.
Broadly speaking, the themes and meanings of the source material are more important than individual events that occur in the story. If the adaptor wants to be faithful to the original work, then it is better for them to focus on maintaining its core ideas – whether that be through depicting a few particular scenes or creating an alternative storyline which can better condense the key motifs – rather than trying to cram in every set piece.
To use a metaphor, stories are a collection of individual stitches which form together to create a single tapestry. When adding or trimming threads, no matter how minor they may seem, consideration must be given to how this impacts the final vision. With the partial exception of stories that have become their own cultural context, changes to the demographics of characters should be more than superficial. If an element is added or removed, then the creator should question how this would affect the development of other aspects of the work.