Belgium could have booked their place on Saturday with an away win in Kazakhstan but played out a 1-1 draw to delay confirming their qualification.
Doku, who was one of Belgium's better players, was particularly critical of his own team's showing.
"It's a lack of efficiency. We didn't win against Kazakhstan, so we absolutely can't be satisfied," he said.
"We've already dropped too many points because we weren't good enough in a large number of matches. Our campaign hasn't gone well, no. Everyone needs to do better. The coach, me, everyone."
The winger suggested the Belgians had got their approach to the match at the Astana Arena wrong.
"We looked at this team and thought they'd play long, but then they played short and started playing football," the 23-year-old said.
"It was a completely different match to when we played them last time. Maybe we didn't analyse our opponent enough. It doesn't matter. We just have to finish our chances and then we'll be done with the permutations."
Doku was also asked by Belgian VTM television whether the absence of players like Thibaut Courtois, Kevin De Bruyne and Romelu Lukaku was a valid excuse.
He shook his head and said: "Kevin, Romelu, Thibaut... if we need them to win against Kazakhstan, then we can't do anything at the World Cup. I think if we want to be significant at the World Cup, we have to be able to win games like this."
Belgium sit two points clear at the top of Group J, and should qualify for the finals in Canada, Mexico and the U.S. in Liege on Tuesday against the tiny principality.