One aspect can ruin the total safety. It can't be more safe than the least safe part of the trip. Sure, maybe in 50 years we'll figure out something better. But SpaceX is talking about flying long haul Earth to Earth routes with Starship, not a hypothetical future craft.
A 747 built 1970 is very different than a 747 built in 2020. Barring PR issues etc, SpaceX could be using an ever improving version of Starship for a very long time.
