Generally, I agree with you. I would take this a step further and say more than having a slight shot at defending, I think DD didn't pull the trigger on "rebuilding" deals at the deadline because the team didn't really have much in the way of tradeable commodities. At least, ones that could be moved without essentially throwing up the white flag on the next 2-3 years, outraging the fanbase, or both. It was (and still is to an extent) a roster with guys who are young and relatively inexpensive pieces to build around (Devers, Benintendi, ERod), young and expensive cornerstone pieces (Bogaerts, Betts), veterans on long and expensive deals that limit the market (Price, Sale, Eovaldi, Martinez), and guys with short-term contracts who were either underperforming their salary or injured (Pearce, Moreland, Porcello, JBJ).
In short, DD might have been able to trade some guys, but it's unlikely he'd have yielded much in the way of prospects. Certainly not prospects that would have elevated the ranking of the farm system significantly.