The Monegasque finished second to Red Bull's double world champion Max Verstappen (25) in the season-ending Abu Dhabi Grand Prix.
"Considering where we were last year, it's a really big step forward," Leclerc said, who won three of the season's 22 races while teammate Carlos Sainz triumphed once.
Ferrari finished as championship runners-up to Red Bull, after ending last year third and without a win. They also drew a blank in 2020, when they were sixth overall.
Ferrari had 12 pole positions this year, the most of any team and 10 more than last season, as well as 16 podium finishes.
Leclerc had been seventh overall in 2021, with Sainz fifth, and this season has been his best yet in Formula One even if Ferrari fans are disappointed the team fell short again.
"I think we improved throughout the end of the season in terms of strategy," said Leclerc, who won two of the year's first three races before his title bid fell apart in a mix of mechanical unreliability, driver errors and strategy mistakes.
"We still need to work in terms of race pace, because on Sunday we seem to struggle a bit more. But we'll push during the winter break in order to catch them back a little."
Leclerc made a one-stop strategy work on Sunday while Sergio Perez (32) pitted twice and was unable to rein in his rival despite an exciting late chase.
"I'm confident that in terms of pace, we will manage to catch Red Bull back next year," said Leclerc.
Team boss Mattia Binotto said the team had succeeded in getting back to being competitive.
"We can put 2022 behind us knowing that we made a lot of progress and, as from Tuesday, we will start preparing for the new challenge that awaits us in 2023," he said.
