The thing is most of his good moves are big moves, and most of his "bad" moves are minor.
I'd say it's a mixed bag tbh, and depends on how you evaluate a trade (value proposition at that moment vs long term outcome)
Karlsson and DeBrincat are imo good, though I guess it's too early to really know for DeBrincat, and the Karlsson trade was a bit of a roller coaster with the SJ pick and Norris' development.
Zibanejad/Brassard, Turris/Duchene, Stone/Brannstrom turned out bad imo, though some will argue the playoff run was worth it in the case of Brassard.
I think some of his minor moves have been pretty solid, Paul/Joseph, Dzingel/Duclair, Dadonov/Holden, getting a 2nd for Paquette/Coburn.
I think the issue with Dorion's trade history is that the bad moves mostly felt avoidable. People rose the red flags the moment Stone signed a one year deal, the Zibanejad deal immediately got criticized for giving up the extra asset with the younger higher upside player, the Duchene acquisition came at a time where it felt like he was trying to save a sinking ship, Stepan trade had people immediately questioning the cost to acquire a guy well past his prime. Maybe these came because of pressure from Melnyk, maybe they are the result of not having an experience sounding board in the room.
The flip side is at least in the case of the Karlsson trade, many people felt it was going to be bad at first too. Got to let things play out I guess.