The hosts strolled to a 4-0 victory at Anfield to move to the top of the Premier League table - at least until Manchester City entertain Brighton on Wednesday night.
Thiago Alcantara and Sadio Mane were both outstanding for Liverpool, whose goals came from Mane, Mo Salah (2) and Luis Diaz.
It left Sky Sports pundit Keane, seven times a Premier League champion with United, fuming once again - or rather feeling blue.
"It was anger earlier in the season, now I think it's just sadness. You look at the United team, there's no heart, no soul, no leaders.
"They are so far off. You look at the United fans tonight, there's no surprise at the scoreline. They kept going until the end, but you just felt Liverpool could score every time they went forward.
"There's just disarray at the club from the top, the board, the fans have no time for the owners. They need a new manager. They need players in, they need players out.
"It's so sad to see and it's not the club I played for. It's chalk and cheese."
Fellow Sky pundit Gary Neville was equally scathing.
He said: "I can't explain how it's gone from slightly promising at the end of last season, finishing second, to the point where we are today, which is an all-time low in my 42 years of watching United."
Colleague Graeme Souness said when looking at the two XIs: "You can't put a Man United player in that (combined) team. That shows you how far off they are.
"Man Utd are a truly enormous club on the world stage and how far they've been allowed to drift off the pace has been exposed tonight once again."
United were behind after just five minutes, Mane beginning his masterclass with a pass which sent both Trent Alexander-Arnold and Mo Salah clear down the right.
The latter took control before producing a low centre which was swept home from close range by Luis Diaz.
Mane's role in the second goal was even better.
A fine Liverpool move was finished off when Mane delivered a perfect pass on the turn which Salah controlled perfectly before shooting beyond David de Gea.
By half time, listless United had failed to manage a single shot - the first time that had happened in four years.
On that occasion - against Manchester City at the Etihad - they actually turned the game around to win 3-2 but despite a brief rally at the start of the second half, a repeat never really looked likely.
Mane put the game beyond them, capping his majestic display with a goal. This time Diaz was the provider with his ball in from the left being guided into the net, first time, by the Senegal international's left foot.
Salah put the icing on the cake four minutes from time, lifting the ball over de Gea after being played in by substitute Diogo Jota.
Liverpool boss Jurgen Klopp gave his assessment of the game.
"I think for 70 minutes we were in charge of the game and for 20 minutes we were not," he told Sky Sports.
"(It was) a really good game and we scored wonderful goals. Everyone is happy."
United manager Ralf Rangnick admitted his side's display was "not good enough".
He said: "We were second best in all relevant areas of the first half and it was just not good enough.
"They showed what kind of calibre they are and right now we are not up to it."
Liverpool ended the night two points clear at the top, with their goal difference also now nine better than City.
They are potentially just 10 games from an unprecedented Quadruple.