The Sox, right now, might be the worst team in baseball. In 3 years they may be the best team in baseball, or they may still be the worst team. The difference is we KNOW they are terrible right now, and a 28 year old 1 - 1.5 WAR player does nothing for the current team.
If Eder puts it together and becomes something, that's a win. If he doesn't, it was still worth it given the state of the franchise and what needs to happen to have any chance to be good again.