Hamilton endured a frustrating weekend in Jeddah, qualifying eighth and then finishing ninth after a gamble to stay out and gain track position under the safety car failed to pay off.
The track layout highlighted the car's below-par performance in fast corners, and Hamilton and his team-mate George Russell were both outpaced by at least one car from Red Bull, Ferrari, McLaren and Aston Martin, effectively benchmarking Mercedes as fifth fastest.
Team boss Toto Wolff admitted there was a "fundamental" issue with the car that meant it struggled on high-speed corners.
Hamilton suggested that it may take some time to improve the W15, and thus there could be some difficult weekends ahead.
"It's going to be challenging in these next races," he said. "I think all the high-speed circuits we are going to be at a disadvantage with the package we currently have.
"But we're good in the low-speed, and some of the medium-speed, we're not so bad. It's just really the high-speed, so we just have to add performance."
He added: "It was like I was in a different category when I was going through the high speed with the other guys around me."
In Jeddah, Hamilton had a battle with McLaren's Oscar Piastri that lasted for many laps, and while he enjoyed being able to race he admitted that he couldn't take much pleasure from the overall result.
"I wouldn't say I'm having fun," he said when asked about his race by Motorsport.com. "I mean, I'm racing for ninth, so I definitely can't say that. Finishing ninth is definitely not fun.
"But I am enjoying the actual racing part. And I was hunting and I was pushing as hard as I could, I was maximising everything I had with the car, I was right on the edge.
"It was just unfortunately really lacking performance in the high-speed, where they were walking all over us.
"But there are positives. The car is good in low speed. We have to add a lot of load in the high-speed. I think if we were able to do that then I think it puts us in the fight. But we've got some work to do."
Hamilton made it clear that he had expected more from the car after the optimism around its launch last month.
"It's frustrating to three years in a row be in almost the same position," he said. "It's definitely tough, but we'll get our heads down and keep working away.
"I know everyone back at the factory is pushing as hard as they can, but we've definitely got to make some big changes. We haven't made big enough changes, perhaps.
"You look at the three teams that are ahead of us and they still have different concepts to where we are in some areas. So we've got some performance to add, that's for sure."
