Les Bleus, who qualified for June's tournament in Poland and Ukraine by topping their qualifying group, produced a couple of mediocre friendly performances in a 1-0 win against the United States last week and a 0-0 draw at home to Belgium on Tuesday.
Blanc's side looked short of invention, failing to create any clear-cut chances against Belgium before being booed off the Stade de France pitch by an angry crowd.
However, they were without playmaker Yoann Gourcuff, who is still waiting to get back to his best after a lengthy injury layoff, as well as injured midfielders Samir Nasri and Abou Diaby and defender Philippe Mexes.
"We need to be better technically," Blanc told reporters.
"We were too harmless, that's an explanation. We have kids like [Maxime] Gonalons, [Yohan] Cabaye, [Marvin] Martin. Youth is good, but limited."
Asked to assess Mamadou Sakho's performance in central defence, World Cup-winning former centre-back Blanc replied: "He's 21, you don't just buy experience in a supermarket."
France, however, are unbeaten in their last 17 matches but next face a huge test with a February friendly against Germany, whom they could also meet in the Euros as they will be in pot four when the draw is made on December 2.
"You know who we could face [in the Euro finals]. The draw will be an important moment. But I spoke with the Germans, they want to avoid France in pot four," said Blanc, who has yet to choose his captain for the championship.
Goalkeeper Hugo Lloris was the captain in the last two friendlies, even against the U.S. when usual skipper Alou Diarra was on the pitch.
The keeper may retain the captaincy as candidate Eric Abidal said he "did not feel it," according to Blanc.
