As long as the organization has and maintain a culture that is aggressively seeking out problems large and small, and proactively fixing aprox. all of them, you will end up with a program with a high rate of operational success.
It's the X-origin vs Slope issue - steeper slope always wins.
The problem is maintaining that aggressive problem-seeking culture after long periods of success
This is part of the culture distinction. On one hand SpaceX is attacking problems, but IMO they often don't go towards attacking the root causal understanding. That means there's a possibility of unknown latent risk.
As an example, they had issues with failures related to their COPVs rupturing. On the one hand, they addressed the problem by redesigning their system. On the other, they never really investigated fully why the COPVs were failing in the first place. Instead, NASA decided to fund that investigation on their own. One possible consequence is that their redesign didn't fully address the risk because they never fully investigated the root cause.
It's the X-origin vs Slope issue - steeper slope always wins.
The problem is maintaining that aggressive problem-seeking culture after long periods of success