Leclerc started from the pitlane in Barcelona after he qualified only 19th and the team opted to make changes to his car for the race.
However, he was only able to rise to 11th place after his SF-23 again performed inconsistently across stints, even when running the same tyre compound.
Team-mate Carlos Sainz also struggled as he slipped from second on the grid to fifth at the chequered flag.
"The first stint we had the hard, which we expected to be a good tyre, but for some reason, it was so bad," said Leclerc.
"Like, no grip at all, especially from the front. The limitations were completely different to qualifying, so today we were more expecting this.
"Then for some reason, the second hard I just do exactly the same thing and it feels really good. So for some reason, we seemed to never really get in the right window of the tyre and when we do it's a bit of a surprise to us. So there is a lot of work we need to do.
"I think where we really need to put all our focus is to try and be more often at the peak of our tyres, and know how to manage them better.
"Two or three degrees makes a huge difference on balance, and this weekend we've been struggling, getting completely outside the window or in the window and happy with the car. So there will be a lot of work on that."
Leclerc insists that he didn't do anything different in the cockpit between the first and second stints, adding: "The thing is that we really did exactly the same thing on both tyre sets.
"And so I will check with the team what we are doing on those two sets that are different between the two sets, and try and understand. But it's very, very difficult.
"As soon as the wind changed slightly we've got a car that still changes quite a lot, so very tricky."
Leclerc stressed that a lack of consistency in the Ferrari on its tyres is making managing races harder.
"It's not like I've got understeer in the car and I can say, 'Okay, this a very understeery car'," he noted. "I've got understeer on one tyre and then you get again, on the same hards, an oversteery balance.
"As a driver, you just did exactly the same things. It's just inconsistencies, but it's very difficult to work on inconsistencies, especially again when you do exactly the same on both sets."
