Mourinho was axed as United boss back in December following a dismal run of results and a public falling-out with record-signing Paul Pogba on the training ground, the Daily Mail reported.
But when asked whether Pogba was the biggest problem at Old Trafford, Mourinho offered a definitive analysis about the deep-rooted issues which are hindering United's progress.
“The problems are there, you can say that these are the players, the organization, the ambition, I only say that I cannot say yes when you ask if Paul was the only one responsible,” Mourinho told L'Equipe.
Following his acrimonious exit, United enjoyed an incredible upturn in results, but its new-manager bounce soon subsided and it finished the season in dreadful form.
Mourinho, following his sacking, said finishing second in the Premier League might have been his greatest achievement in management.
It is a statement, he believes, has now been proven correct following the conclusion of this season.
“I said nine or 10 months ago that after winning eight championships, finishing second with United may have been my greatest achievement,” he added.
“Now people understand.
“I do not always do my analysis publicly on Manchester United. I do not want to talk about it and I have the feeling that I do not need to speak, that time gives explanations.
“About United I want to say only two things: One is that time has spoken. Two is that the problems are still there.”
Mourinho was sacked in December after a disappointing start to the season saw United fall way behind their top-four rivals.
After a 3-1 defeat by Liverpool at Anfield, United was sixth in the table and 11 points behind fourth-placed Chelsea.
His final six months were undermined by squabbles with the board over transfers, with Mourinho denied the funds for the center back he craved.
And there was the public fallout with Pogba, who was stripped of captaincy duties after criticizing the team's tactics.
In two-and-a-half years at Old Trafford Mourinho lifted the League Cup and the Europa League in 2017.