Beane reached the postseason 4 consecutive times, twice getting eliminated by the eventual WS champions in the first round. The A's also won 3 division titles in 4 seasons, with the one team that didn't still winning 102 games. Going 4 straight times and winning 100 games in back-to-back seasons are two things Beane's teams did that the Red Sox have never done.
That he never won the World Series sets a pretty high bar for failure. In those 4 seasons, the Oakland A's under Beane were a successful franchise using any other metric.
Now, it is a pretty big IF, but again, if they can do it, what is the problem? Would you prefer a low payroll team that makes the post-season 4 years in a row, or a high payroll team that misses the post-season altogether most seasons?