Senegal succumbed to a 3-0 defeat to the Three Lions at the Al Bayt Stadium on Sunday.
The African champions matched England's intensity for much of the first half but Jordan Henderson's goal against the run of play and Harry Kane's first goal of the tournament on the cusp of half time turned the game in the Europeans' favour.
Bukayo Saka put daylight between the two sides with a third goal in the second half.
England have now set up a quarterfinal meeting with defending champions France but Koulibaly does not discount the chances of Gareth Southgate's side.
"They are very good. We know that they have a lot of talent, a lot of big players, we know all of them," Koulibaly told reporters.
"They played very well, they can go far, but the next game will be tough against France. I hope the best will win.
"They have so many options but we know every game is different in the World Cup. You can score a lot in one game and then the next one will be difficult to score.
"They have to keep going and believe it, I think they can go far."
Koulibaly was content with Senegal's progress in Qatar after losing star player Sadio Mane on the eve of the tournament.
He said: "It was a beautiful tournament for us. We wanted to get out of the group stage, we did it, and now it was a tough game against one of the best teams in the world. We can be proud of what we did."
Koulibaly's Chelsea club-mate Edouard Mendy added: "Dealing with defeat is not difficult. We came up against a better team than us, we have to accept that, England played at their best.
"They also had all their players at their disposal while we were missing some key players. We had to play without Sadio. We also had Idrissa [Gueye] and Cheikhou [Kouyate] missing.
"So when you play against a team like that with key players missing, it is complicated.
"But throughout the tournament and throughout the year, we have shown that Senegal is more than 11 players, it is a group.
"We will continue to move forward, to progress and we will come back stronger in the 2026 World Cup, God willing."
