Yes, baseball teams must evaluate what players have the best athletic ability in order to remain competitive. Remaining competitive is important because the income of every player is dependent on how many games are won. By forcing an older player to step down, this allows room for a better performing rookie to strengthen the team.
Prince Fielder has now retired after a long and storied career. It was definitely time for him to go. All baseball players should be required to retire after a certain amount of time, just for their own health and safety. The move will also help baseball teams revitalize themselves if they are lagging.
Yes, baseball players should be forced to retire. There comes a point in every player's career where they no longer can contribute to the team. At that point, the player should either retire, or the team should fire them to make sure that the team can survive. The player can continue their involvement in baseball, however, by being a coach, or by being involved in the team's leadership.
They should not be forced to retire just because they have reached a certian age. Instead, they should be given the same respect as anyone else and allowed to retire when they are no longer performing at a level that is required for the team to do well. Like any other sport they should be able to be let go at the end of their contract.