Ben (or Larry) made some serious mistakes signing Pablito, HRam and Castillo, but Ben was handed a team in turmoil, a horrific manager thrust upon him and some massive contracts for under performing pitchers.
On paper, the rotation Ben was handed looked great. I find it hard to blame him for them not pulling their weight in his first year. He then wins a ring then ends up trading away some beloved Sox pitchers. People blamed him for trading away the under performers or "clubhouse cancers," (which in itself is debatable).
3 of his teams under performed. GMs are ultimately to blame, and Ben deserves much of the blame for at least 2 of those 3 bad seasons, but he wasn't handed the farm DD was. He pulled off one of the greatest trades in ML history by dumping CC, and Beckett & AGon swiftly declined afterwards, so when judging a GM in hindsight, as they always are, we should take that into account. Without that trade, we wouldn't have had the budget space or talent to win in 2013. That trade also freed up money into DD's regime, although the HRam/Pablo/Castillo deals more than overshadowed those savings.