Seven-times world champion Hamilton, winner of a record 105 races, was hard on himself after qualifying 12th at the last race in Hungary before the August break while teammate Charles Leclerc secured pole.
The 40-year-old has yet to stand on the podium for the Italian team.
"Of course he's talking nonsense when he says something like that because he's the greatest driver of all time," Russell told reporters ahead of the Dutch Grand Prix.
"He's still an exceptional driver, we saw it -- he obviously won the sprint straight away at the start of the year in China," added the Briton.
"He's still clearly got it but Formula 1 is not an easy sport especially if the team is not performing at the highest level that compounds the issue. Of course, Charles is an amazing driver too.
"I think right now, 14 races down, probably every driver bar two are looking forward to 2026 and for a fresh opportunity to fight for a championship. For someone like Lewis, that's what he lives for, not just getting in the points."
Russell is set to stay at Mercedes next year but has yet to sign an extension to the contract that expires at the end of the season.
He said before the break that there was no rush and that had not changed.
"It's moving in a positive direction," said the fourth-placed driver. "I think we're getting closer to being on the same page with a few things.
"But I think as there is no time pressure from the team’s side, and no time pressure from our side, we’re sort of just ensuring it’s done properly."
Mercedes had been interested in signing four times champion Max Verstappen from Red Bull but the Dutch driver has said he will be staying.
"There's pros and cons into having short term, long term," Russell said of the duration of any extension.
"Of course, I'm 28 next year, I'm still feeling pretty young but at some point I need to make sure everything is right and we're all heading in the right direction. I hope that can be with Mercedes."