While I am unfamiliar with your collective agreement, most unions run by seniority. It would stand to reason that the older writers would be more likely to survive a layoff than newer ones.
Members who feel that their union is not fulfilling its mandate should have access an appeal or complaint process through their union or can complain to the Labor Department of the jurisdiction they live in.
While I can not speak to the particulars of your situation, unions are strong advocates for workplace equality including the rights of racialized workers, women and the disabled. Unions are the first party to champion pay equity and accommodations for disabled workers.
None of this necessarily means happy endings for everyone. Unions themselves fall prey to the same problems other workplaces have. It just means that workers get due process they wouldn’t enjoy in a non-unionized environment.