The dramatic triumph has seen Leeds move to within one point of leaders St Helens.
"I'm not happy at conceding 31 points, but we were playing a very good Catalan team," McDermott told BBC Sport. "I'm comfortable with the win.
"We scored more tries than them and, while we weren't great and while I had resigned myself to the loss and we feel fortunate to have won, I'm not ashamed either."
Leeds continue their Super League campaign on Friday with a trip to Wakefield Trinity Wildcats.