Manchester United has been playing poorly since the beginning of the season, and you are claiming that
Even if there is a chance of qualifying for the last 16, the result will remain the same because basically the team led by Erik ten Hag is not yet mature in Europe's highest competition. I think their chances are less than 20% to qualify for the next round and they will still be at the bottom of group A.
This outcome aligns with Manchester United's current performance. Bayern Munich is almost certain to take the top spot in Group A. If Galatasaray loses to Bayern and Copenhagen defeats Mu, the competition for the 2nd place will become quite intense.
But we have to admit that Arsenal has still two games to go in the group that should by no means underestimated and could still get them into trouble if they lose them both or do not win them both to be more precisely. The game away against Sevilla and PSV Eindhoven will be harder than many may think I believe. Beating Sevilla in their home stadium has turned out to be a very diifficult task and despite the crisis that Sevilla is going through, I expect it to be hard again this season also for Arsenal. PSV has been beaten 4-0 in the first game, but lots of things worked out well for Arsenal. It wasn't as one-sided as the final result may suggest.
It won't be too difficult for Arsenal to secure a victory against Sevilla, even though they're playing away from home. Arsenal's fate is still in their own hands.