Ten Hag has often defended his side this season, despite their lack of consistency and array of goals that they have conceded throughout 2023-24.
However, that was not the case after the debacle at Selhurst Park, as United conceded twice in each half as Palace recorded their first-ever Premier League double over the Red Devils.
Michael Olise and Jean-Philippe Mateta netted during the opening 45 minutes, before Tyrick Mitchell and Olise got on the scoresheet during the second half.
As a result, United remain in eighth position in the Premier League standings, but now with a negative goal difference having shipped 55 goals from 35 top-flight fixtures this campaign.
'Manchester United should perform better'
United allowed Palace a total of 18 goals on goal, 10 of which that were on target, while the visitors to the capital created just seven opportunities.
Rasmus Hojlund was unfortunate to have a goal disallowed for a foul on Dean Henderson that would have made it 1-1, yet Ten Hag opted to make few excuses for his team's under-performance.
Speaking to Match of the Day, the Dutchman said: "As Man Utd we should perform better. The players who were available should do better. It's a deserved defeat. The performance wasn't what we expected.
"We have to focus on the team performance. This was not right. We have to put it right on Sunday. We have to learn from this game and improve.
"You have to stick together. You have to take responsibility. The fans gave us such huge and tremendous support."
He added: "I will keep fighting and I prepared the team in the best way I could do and it was not good enough, by far not good enough. I have to take the responsibility for that, but I will find energy and I will prepare them for Sunday's game.
"All season, we have huge problems and by now, this is the fourth defeat in this calendar year, so that's not a lot and every time, we had huge problems and many times, we sort it out. Today, we didn't."
What next for Man United?
United now have almost a week of preparation ahead of welcoming Arsenal to Old Trafford on Sunday, Ten Hag's side remaining adrift of Chelsea on goal difference
If Chelsea are able to defeat Nottingham Forest a day earlier, United face the prospect of requiring a minimum of four points from their final three games to have any chance of reclaiming seventh spot.
That is also dependent on the results of Newcastle United, who only sit two points above United in sixth when the two teams still have to play each other three days after United face Arsenal.