Without trying to get into another "cliff"/"DD killed the farm" discussion...
MLB Pipeline's midseason update to the top 100 prospect list features two former Red Sox farmhands - Michael Kopech at #13 and Logan Allen at 90.
Kopech has a 4.28 ERA and 1.36 WHIP while walking over 5 batters per 9 in Triple-A - he's got a great arm, obviously, but is not someone I'm shedding tears over trading for possibly the best pitcher on the planet.
Allen would be nice to have right now, and it's still kind of a bummer that he was the third piece in that deal. That said, would anyone really take that trade back now if they had the chance?
Other than that, all the prospects Dombrowski traded are either in the majors and scuffling (Margot, Moncada), hurt (Espinoza), or not top 100 material to begin with (Basabes, Dubon, and so on), so even if you could go back and rescind all of his deals, whether our farm would really look much better than it does now is highly dubious.
The main reason our system sucks this year is that we've graduated a lot of impact talent in recent years (Benintendi, Devers) and have largely failed to replace it, which is an issue that dates back before Dombrowski...the changes to the old system that allowed us to throw our financial weight around in the draft and international market to land better players have a role in this. We were in the penalty box for international amateur signings for a couple of years due to the money we spent bringing in Espinoza, Moncada, and others - and then had what prospects we were able to sign taken away one of those years due to tomfoolery in the foreign market. We've also suffered a rash of injuries and general bad luck beyond any GM's control (Groome TJ surgery, Chavis' PED suspension, a potential stud catcher in Daniel Flores suddenly passing away from cancer), and though recent drafts have brought in some interesting talent, much of it is still too raw and far away to be counted on for anything yet.
All of which is just to say that I think blaming our current thin farm on "Dombrowski trading all the prospects away" is an overly simplistic way of looking at the situation.