The Old Trafford captain, who has played through enough European campaigns to separate the good from the bad, has given a thumbs down to the latest never-ending format.
Keane and his United team-mates won through as the Group B winners without finding their best form - mainly because they did not have to. "The buzz hasn't been the same. If you lose a game you can still get back into the competition," the Manchester United midfielder said.
"In the past if you lost that was it, you were out. The intensity isn't there any more in these matches. It's been hard to get going. The home games have been disappointing. We've had to grind out results.
"If we play like we did against Sturm Graz when we meet the top teams we would be beaten. We've not been firing on all cylinders but we're in the next stage in Europe. However, we know we need to improve."
Keane predicts that United's slow-burn season will ignite when the opposition provides a bigger challenge. "We've not played great so far but we've not played badly either," he said. "But remember there is a lot left in the team. There are one or two [injured players] to come back. Our training is designed to help us hit our peak later in the season. I don't mind the number of games, because we would only do more running if we weren't playing. We know we will have to raise ourselves against the better players. You don't get the ball back so quickly if you give it away.
"But those games bring out the best in all players and they also excite the fans. It's been quiet at times in Europe this season, but it's also up to us to get the crowd going. United are now in the last 16 as one of the top four seeds and have avoided a draw against Barcelona or Lazio, the two sides we fear most."
However Keane, who has a massive few months ahead of him concerning his future at the club, knows United will have to beat that calibre of side eventually to hold on to their trophy. "Barcelona will be there or thereabouts at the end," he said. "They seem to be hitting form, but hopefully we will do the same later on. We're pleased not to meet them just now but I'm sure they will be happy to avoid us, too. If we had been in the same group it wouldn't have bothered us."
Ole Gunnar Solskjaer, the Norwegian striker who produced his first European goal since last season's final against Bayern Munich in Barcelona when he netted in the 56th minute of Tuesday's 2-1 win over Sturm Graz, said: "Of course it was a nice feeling to score again. I enjoyed myself and had a few chances and should have scored before. But who cares now? I hit it quite cleanly, and it was great to see it go in. We had to win tonight and we want to be the best and win every game.
"As for the next stage, if you want to win it you have to play the best anyway at some stage, so it doesn't really matter who we meet in the next round - so let's just wait and see."
Solskjaer, a spectator for most of this season, needed a lift and says his volleyed goal has done the trick. "Obviously it gives me confidence," he said. "I've been training hard, and so this helps my morale.
"You want to play in as many games as possible. But it is a squad game, and I will play my part whenever I'm needed. You always want to be called up for every game, but that's the manager's decision."
The BBC will broadcast live coverage of United's World Team Championship challenge in Brazil. Sir Alex Ferguson's team will play the Brazilians Vasco da Gama, the Mexicans Necaxa and South Melbourne of Australia in the group stages of the new Fifa event, which begins on 5 January. All three games will kick off at 8.15pm UK time and will be shown on BBC1.
The BBC's Controller of TV Sport, Mike Miller, said: "We are delighted to be bringing Manchester United's quest for world domination to millions of British fans in prime time."