While it's true that not all teams are equal, whether it be from the perspective of finances or talent—both on the major league roster and in the minor leagues—every team has the ability to make a move.
It's an ongoing battle, and kind of a crap shoot, to determine if a player available via free agency or trade is a better fit, a better option, than what a team currently has.
The temptation of making a move can be overpowering and unrelenting.
In some cases, resistance is futile.