I think it's a mistake to combine past, present and future discussion, especially given the major changes in the past decade in terms of statistical analysis (launch angle, spin rates, a million other things) plus the multiple different CBAs that teams have been operating under. My quick perspective from the other side of the rivalry:
Past: Obviously the past 18 years since John Henry bought the team have been deeply successful overall, 4 WS championships since then is the most of any team in MLB.
Present: They are coming off the best team in franchise history and a dominant postseason run, they basically reassembled the same team and it hasn't worked, but still it's hard to complain here IMO given any big picture sense.
Future: This is the concern, and this is where IMO the past starts to matter a lot less.
@Sandy Leon Trotsky says "I wouldn't be surprised in 2 years or so that the Sox end up having a top ten system" but that doesn't seem to be based on anything other than a belief that these things naturally go in cycles, sometimes they do but sometimes they don't. The Dodgers and Astros and Yankees are attempting to build personnel not just for now but for the longer term, the group of minor league pitchers that the Yankees currently have on the way (Deivi Garcia, Clarke Schmidt, Luis Medina, Roansy Contreras, Luis Gil, Miguel Yajure, Mike King) would scare the crap out of me as a Sox fan, not to mention the highly touted Jasson Dominguez. This is where the Sox seem to be falling behind badly, not just NY but TB and HOU and LAD and other teams also, this is what would deeply worry me if I were a Sox fan. How many of the 29 other organizations would swap talent with BOS right now, majors/minors combined, including salary commitments and spending power? I think less than half.