It was a very bad performance by United. It's not like they lost due to bad luck, Fulham looked better than them in that game.
It's pretty clear that they're lacking in the attack department, they only have 36 goals scored, while any of the top 3 has around 60, so that's a huge gap. They have the least goals scored in all the top 12 in the table.
Ten Hag will have to start making changes or he'll be on his way out. Fans could have been somewhat satisfied with the 3rd place last season (despite finishing 14 points behind the City), but not even making to the top 5 will be a disaster for the 3rd richest club in the Premier League.