"Natural evolution" implies that everyone experiences a process of development that is unique to them, and makes them who they are (and, by extension, continues, and continues to enable them to become who they will be in the future). That path is definitionally different for every person, and includes environmental factors, genetic factors, epigenetic factors, psychological factors, and much much more. In short, that path is inherently complex and unpredictable.

So why does that exclude gender affirming care for others? That your path and history doesn't include the need for, eg. hormones or plastic surgery, doesn't mean that's true for every possible variation of development? And remember, every elective breast augmentation, hair bleaching, manicure, lip plumping, etc... is a form of gender affirming care.