I almost hate to admit it, because he was such a putz. But you can make the argument that no commissioner in history ever corrected problems in his sport as well as Bud Selig did.
Between the wild card, CBA changes, and revenue sharing, MLB has probably never had a moment in its history where so many teams can reasonably expect to contend in a short period of time.
The Pirates are just mediocre and not God awful even after Andrew McCutcheon was stolen by aliens and replaced with some kind of strange duplicate AND their third baseman got arrested as some kind of international human trafficker AND their current best player got busted for being hopped up on goofballs.
It’s been a fun year for the Buccos......
The next big challenge (already underway) for the sport is managing a cultural/generational transition where it turns from an "American" sport to a "foreign" one. Baseball talent here in the U.S. has declined a lot in recent decades, and you can already see signs that baseball is slowly being relegated to the same level of public attention as soccer. This is not a new thing, but you're starting to see the inevitable change that has come about as football and basketball eclipsed baseball as the preferred sports for American-born youngsters.