Aldridge branded United as the "worst" United team to win at Anfield.
He wrote in the Liverpool Echo: "In over 60 years as a Liverpool fan, player and commentator, that is the worst Manchester United team to ever come to Anfield and win. They are bang ordinary and the fact that they emerged with a 2-1 win on Sunday night tells you that there is so much wrong right now.
"In years gone by, United have won away at Liverpool with some greats of the game. The likes of Wayne Rooney, Paul Scholes, Roy Keane, all the household names who were major stars at Old Trafford. And sometimes, you had to just hold up your hands and say they were the better team.
"Ruben Amorim's team have been generally awful though. They finished 15th last season in the Premier League and the fact they have beaten the champions on their home patch will be cause for real concern for Arne Slot and his staff.
"I've been there as a manager, at Tranmere Rovers, when you are struggling and can't see the wood for the trees. That is when you need your staff to guide you through, people whose opinions and expertise you can trust. Slot has that in abundance behind the scenes, I'm sure.
"But right now, Liverpool need to grind out a victory from somewhere quickly. They need clean sheets and need to start defending properly. That is something they are not doing now and I've said it a few times in this column of late that the team needs to start doing the basics properly."