Jurgen Klopp's side eased to a 3-0 victory over Maribor on Wednesday, with Mohamed Salah, Emre Can and Daniel Sturridge on target in the second half at Anfield.
The triumph marked the second time in a week the Reds have gone in level at half-time before scoring three goals after the break, with their Premier League win over Huddersfield Town coming in identical circumstances.
Liverpool are now just one win away from reaching the Champions League knockout stages, but Keane was not impressed with their performance and believes they are going "nowhere fast".
"It's hard to figure out Liverpool at the moment," he told ITV . "It's hard to get excited about them. To me, they are going nowhere fast.
"They're neat and tidy, but defensively... come the end of the season when the prizes are being given out, Liverpool will be nowhere near them.
"If Liverpool were playing out in my back garden, I wouldn't watch them. They're just drifting. Drifting nowhere."
Klopp's team currently sit sixth in the Premier League table and visit struggling West Ham on Saturday in their final match before the upcoming international break.