People focus too hard on the idea of a team winning and losing a trade.
This wasn't a dynamic where Ottawa could have kept Debrincat, but they chose Kubalik and a late 1st over him. This was a dynamic where Debrincat had one foot out the door, and he would only sign with one team. Ottawa was not in a position to keep him through the season without it becoming a distraction. The salary cap made it difficult to move players. Debrincat refusing to sign anywhere but Detroit made it difficult to create a market for him.
The return on paper is bad, but when you consider the realities of the situation, none of this should be a shock. Kubalik was a throw in, who became less relevant as soon as the team signed Tarasenko. The Garrioch media spin was that he was the centrepiece of the trade, and a top 6 forward.