I associate Steve’s line “I can save today, you can save the world” with present day Diana even more so than past Diana, honestly.
Diana in present day is still trying to save the world. She went back to Gotham to fight Doomsday in BvS. She’s helping Bruce form the Justice League. She’s fighting Steppenwolf’s army. Steve’s words really ring true for Diana in the present. Steve made sure the world war ended when he blew up that plane, and Diana is still honoring his memory by continuing to try to save the world.
It wouldn’t surprise Steve at all that one hundred years later, Diana is still fighting.