The French club triumphed 2-1 at home to advance past Mlada Boleslav 6-2 on aggregate but Fournier was far from satisfied after the match.
Lyon moved into the play-off round of the Europa League's qualifying system but Fournier argued his team lacked spirit and blamed complacency for their performance.
"The satisfaction comes from having won and having qualified. We can stop there with the satisfaction," he said.
"It was a laborious match that we started badly. We lacked mobility around the man on the ball.
"There was a lot of wasted balls and that made it easier for the opposition defence to organise itself and so they didn't allow us to get our game going.
"The first-leg score [Lyon won 4-1] could explain it. That is what I feared. We were already almost through and there was not that extra bit of spirit which you need in European matches to make things a bit easier."
After a scoreless first half at the Stade de Gerland, Lyon extended their aggregate lead when Alexandre Lacazette scored in the 58th minute.
A penalty with 19 minutes remaining from Florian Milla saw Mlada draw level on the night but Lyon eventually won thanks to Clinton N'Jie's 89th-minute strike.
But Lyon's progression was tarnished by injuries to defenders Henri Bedimo and Lindsay Rose (both hamstring), and skipper Maxime Gonalons explained the former looks set to be out for an extended period.
"We are going to lose Henri for several weeks. It is less serious for Lindsay I think," Gonalons said.
Lyon's next fixture will be against Rennes in their Ligue 1 opener on Sunday and veteran defender Christophe Jallet hopes the performance against Mlada will spark Fournier's side.
"It is a victory, undoubtedly not the most beautiful but it is important to win your matches even when it is a bit more difficult," the full-back said.
"This should give us a kick up the backside. We will need to be at 100 per cent or even 120 per cent to have a hope of winning on Sunday."
