Team rebuilds do sound like a logical solution in principle. The long-known Detroit Tigers formula has been this: lose in the short-term by trading away major league assets in exchange for future talent, acquire high draft picks as a byproduct of losing, then start to spend on complimentary major league free agents when those trades and draft picks begin to yield major league returns. In baseball, however, prospects can be difficult to project; making any return in trades or any draft pick at a considerable risk of contributing little-to-nothing at the major leagues.
This makes the front office, particularly the General Manager, the most important position within an organization during a rebuild–considering they will be the ones negotiating these high-risk, high-reward deals and selecting amateur players they hope can either provide value via trade or can contribute at the major league level.