I think the reason why Dragon never tried to save Ginny, Iva, or Kuma was because unlike Luffy, who lives only for himself, Dragon has dedicated himself to a movement that is greater than himself.
He can’t just recklessly try to save his friends, even if he wants to, because that would endanger the movement. Dragon is the leader after all.
However, what is different now is that unlike before, Dragon has a successor: Sabo.
With Sabo’s newfound fame as the flame emperor, it was stated that his notoriety even rivals that of Dragon.
This makes it the perfect time for Dragon to step aside to save Garp.
We would get development with Sabo becoming leader of the revos, and development with Dragon finally putting the movement aside to save his family.
He can’t just recklessly try to save his friends, even if he wants to, because that would endanger the movement. Dragon is the leader after all.
However, what is different now is that unlike before, Dragon has a successor: Sabo.
With Sabo’s newfound fame as the flame emperor, it was stated that his notoriety even rivals that of Dragon.
This makes it the perfect time for Dragon to step aside to save Garp.
We would get development with Sabo becoming leader of the revos, and development with Dragon finally putting the movement aside to save his family.