50-70% defect reduction is significant, though.

It is true that black hats are going to focus on the remainder pretty much by definition because there’s no other choice. The rest is a problem and it needs a solution. But the fact that it exists is not a sound argument against choosing a memory-safe language.

Current solutions are not ideal but they still eliminate a huge portion of defects. Today we can avoid all the memory issues and we also can focus on the next biggest category of defects. If we’ll keep halving possible defects it won’t take long before software is near defect-free.