Having led France 10-7 on Sunday, Canada was a converted try away from taking the lead when trailing 25-19 in the second half with the French struggling to handle the pressure at a rain-soaked McLean Park.
But the Canadians conceded three tries in the closing stages of a 46-19 defeat.
"We had reasonable patches, but we can't afford to do that at this level," Crowley said. "If you accept it you won't improve."
Canada also missed two penalties and a dropped goal when clearly in the ascendancy midway through the first half. Those misses proved crucial as France rallied to lead 19-10 at the interval.
"It was very disappointing from our perspective. We were nine points behind at halftime and lost 14 points in the last five minutes of the second half," Crowley said. "The guys have played well but you're only as good as your last performance, and our last performance was a loss."
Crowley was delighted with how his forwards matched France for long spells in the scrum, but lamented that the "last five minutes of each half killed us" in which France scored the majority of its points.
"You can't question the emotion and commitment from our guys, but you just can't fall off in the last bit," said Crowley, a former New Zealand international.
France prop Jean-Baptiste Poux praised Canada's physical commitment. He was testament to that, twice leaving the field to receive treatment to cuts under his left eye and on his chin.
"They were good, they were rigorous and made the most of the weather conditions" Poux said. "They used the high ball well, and you could see that they are not an easy to play against. They didn't beat Tonga for nothing."
Poux's opposite number, Hubert Buydens, thinks France could have lost the game if not for Canada's missed chances.
"You don't play the game if you don't think you can win. A couple of goal kicks and it could easily have gone the other way," Buydens said. "I think it's just how you play the big matches. If we had the same calibre matches every year you could easily learn how to finish it off."
France had a side packed with experienced players from its prestigious Top 14 league, while Canada's team was comprised mostly of amateurs and looked tired in the last 20 minutes, when Vincent Clerc completed his hat trick with two late tries.
"I thought we played quite well, we hung well with them for the majority of the game," Canada flanker Chauncey O'Toole said. "I think one of the hardest parts with the fully professional outfits like France is that these guys are more battle-tested, playing these games every week in the Top 14, English Premier League. Whereas for our lot of our guys we're lucky to get half a dozen of these games every year, so it makes a big difference."