The Red Devils were initially forced to come from behind after David De Gea failed to deal with Shkodran Mustafi's header, while in the second half, the ball trickled in off Marcos Rojo as he attempted to challenge Alexandre Lacazette.
Per the Daily Mail's Chris Wheeler, he said:
"We drew 2-2, but we scored four goals. As always we made mistakes, and we paid for the mistakes. Even in matches like today where we played well we always shoot ourselves.
"Our problem is a having performance like this without the mistakes we made. ... We are always punished."
The manager added that he was pleased "with the spirit, the effort, dynamic, intensity," but "even from our bench, you could feel the little panic when the ball comes to our defensive third."
He echoed those comments to BT Sport's Des Kelly after the match:
Despite being pleased with aspects of the performance, Mourinho also appeared to criticise his players' technical quality at the end of his interview.
"It's a positive sign, but there are things that I cannot get from them, and I cannot say much more than this," Mourinho said (h/t Goal). "I prefer just to say that I'm happy with the soul, the commitment the bravery—I'm really happy with that."
It was the fifth time in the Premier League this season that United have taken something from a match after going behind.
They've shipped 25 goals in the Premier League this term, which football writer Daniel Storey put into perspective:
The Evening Standard's James Robson noted one of their problems after Mustafi's opener, which came from a corner:
Resilience at the back has often been a hallmark of Mourinho's teams over the years. That he has failed to instil that quality in his United side is a worrying sign for the Red Devils because their defensive vulnerability has hardly been a byproduct of a swashbuckling attacking approach.
As for his implied criticism of his players' talent, the Special One has spent close to £400 million in the transfer market since his arrival at the club in 2016.
If the players he brought in aren't capable of meeting his demands, the fault lies with him.