Having seen one or more family members suffer for years from Alzheimer's, I'm inclined to agree with you to an extent. Dementia is not a desirable end state. But I think the parent's point is also very important. Those family members also had other things killing them at the same time, so it was really a race between diseases.
We need to fix aging (and address the cultural belief that it's necessary), we need to cure cancer and heart disease, etc. Postponement, if it distracts researchers from the real goal rather than acting as a necessary stepping stone, is ultimately counterproductive.