Baseball is the greatest of games because it is the most democratic and is played at its basic core the same way it was one hundred and fifty years ago. You can't get a Jack Taylor of Grinnell in baseball. Everybody in the lineup must take his turn in proper order.
That said, the game continues to evolve in many ways. The baseball itself is dead and then livened. You could throw a ball with tobacco juice slathered on it until you couldn't. An entire game between St. Louis and Brooklyn in 1908 was played with one baseball; today a typical game requires about 70 baseballs, all with nary a scuff or mark. You couldn't have an instant replay 20 years ago because some games were not even televised, or crudely so; today every game is produced in riveting high definition.
Think of baseball as a living thing, an organic garden. It still needs care and weeding and pruning to flourish. Baseball is overdue for some pruning -- nothing too major, but changes to the rules of how the game is played to keep it going strong while still honoring its heritage.
When it comes to areas of improvement, I've come up with a starting nine: nine rules changes baseball should implement immediately.