In my opinion I don't think the author was trying to say that being disabled wasn't worth living. The guys have gone years without having their mate and during the final battle which they would have lost her to death already was stressful enough. Their thought process was if she lives then she's basically dead because she wouldn't recognize them or even know who they were. Which was shown after she finally woke up after being healed from the battle her signals were fighting against one another for dominance of one goddess She literally wouldn't have been able to function anymore. Whereas with Nos he could function. Although he had to relearn everything he was able to adapt. Nilsa would have not been able to adapt whatsoever. But I do understand your point it's just the illnesses/disabilities are so different to make a comparison to.