Elkann’s remarks reflect the frustration and disappointment at Ferrari, who came close to becoming constructors’ champions last year but have failed to win a grand prix this season.
But they are said to be meant to be taken in a constructive way as a spur to improve.
McLaren, who beat Ferrari by only 14 points last year, won the title with six races remaining this season.
The constructors’ championship determines the teams’ prize money and each position gained close to the top is worth approximately $10m (£7.6m) over the place below.
Leclerc said on social media it had been a “very difficult” weekend in Sao Paulo – Ferrari picked up only six points overall, thanks to Leclerc and Hamilton finishing fifth and seventh respectively in the sprint race.
Leclerc added: “Disappointing to come back home with nearly no points at all for the team in what is a critical moment of the season to fight for the second place in the constructors’ championship.
“It’s uphill from now and it’s clear that only unity can help us turn that situation around in the last three races. We’ll give it all, as always.”
Hamilton won the sprint race in China at the second race of the season but is yet to stand on a grand prix podium.
Leclerc – who qualified third in Sao Paulo at the weekend but was taken out of the race in a crash with Mercedes’ Kimi Antonelli after the Italian collided with McLaren‘s Oscar Piastri – has scored seven podiums, with a best result of second in Monaco and Mexico.