Norris had been upbeat about challenging for victory at Suzuka after qualifying third fastest but on race day the Briton was nowhere near the two Red Bulls, who finished 1-2, and finished fifth behind Ferrari's Carlos Sainz and Charles Leclerc.
"Ferrari are clearly ahead, they've been ahead all year," Norris told Sky Sports. "They're still ahead. We've not changed anything. There's no reason why we should be ahead.
"It doesn't feel great when you start third and just kind of go backwards and kind of feel like you're just fighting a bit of a losing battle against these guys.
"They can just do a lot more, you know. It's hard to fight on a track like this, but we gave it a good shot."
Norris was in Leclerc's rear-view mirror for a large portion of the race before he was overtaken by Sainz on the 44th lap.
The 24-year-old said he was not convinced about McLaren's decision to have him pit at the midway point of the race when he was hot on Leclerc's heels.
"This is something we'll discuss after in the briefing," Norris added.
"Maybe a discussion of if we could have done a better job for people but it's always difficult to make those decisions at the time."
Norris is fifth in the drivers standings, 18 points behind Sainz in fourth.
McLaren team principal Andrea Stella said the result in Sunday's race was a fair representation of the order of competitiveness this season.
"We did try to go for the podium by stopping early, making sure that we could keep the position on ahead of Carlos," Stella said.
"But ultimately we saw throughout the race that there wasn't enough pace in the car. That's fair enough ... we have upgrades coming so we keep going."
