By raising the floor of production Dipoto took a weak system and a 74 win team, added depth to the farm already while improving by 12 wins. If the focus continues on improving what's upgradeable and there's still improvement on depth and getting younger at the same time, why can it not continue?
Some mistakes have been made but in total the last year and change has seen improvement to nearly everything about the team without having a pythag strange win total. Pythag was a win above the actual total on a team that had 1 Starter miss less than 8 starts, only 3 that made more than 20 and the general meltdown of Miley. Several younger and controlled players were brought in while not trading any known valuable stars. To say that it can't be done is to ignore Karns, Powell, Gamel, Heredia, Vogelbach, even Martin (27 when acquired) and several minor leaguers who could make impacts in the next few years.
The history you use as evidence is from GMs who have never done what Dipoto has so far (including Pythag being nearly even;2009 Pythag: 75 wins, 2007 Pythag:79 wins). To say Dipoto is limited to their resumes seems like selling him short.