Makarov alone could not save Port Arthur

Could Admiral Stepan Makarov have significantly changed the Russo-Japanese War if he survived the mine that killed him?

Probably not by himself; Port Arthur's supply and siege timetable mattered more, and relief by Rozhestvensky would still arrive too late.

Makarov's survival probably would not change the siege because the Russian force still faced acute supply and timing problems. A real Japanese dilemma would require Rozhestvensky's Baltic fleet to arrive before Port Arthur fell, an unlikely schedule given the Japanese Army's rapid campaign. The later Russian habit of turning the safely dead Makarov into a hero and Rozhestvensky into a convenient villain is challenged here. Rozhestvensky's achievement was getting an initially poor force across the world, supplied and trained well enough to land hits at Tsushima, even though it remained unable to win.