The French led the quarter-final 16-0 at half-time and despite a fight back after the break, Johnson's men slumped to a 19-12 defeat in Auckland.
"I'm proud of the way they came back but at 16-0 but we gave ourselves too much to do," Johnson told ITV Sport. "They scored their tries early and we were chasing."
However, the coach believes that there is reason to be optimistic where future tournaments are concerned.
"This team's best days are ahead of it," added Johnson. "The core of them are very young playing at their first World Cup.
"But they will be far better as we go into next year."
France will now play Wales for a place in final next Saturday after Warren Gatland's side advanced past Ireland this morning.