The Manchester United team has only been built for a few seasons by Ten Hag and it is very different from Manchester City, I don't think it can be compared and in the future I still believe that if Ten Hag continues to make improvements and cover up the mistakes that have occurred then it is very likely that the Manchester team will United will be perfect again or match Manchester City's level for the title competition.
But, Ten Hag only have a year to build Manchester United, I don't think he can. If Manchester United didn't qualify for Champions League in the next season, I'm 100% believe they will sack Ten Hag ASAP. And then, the problem can't be resolved since the team always change the team for every one or two years.
The best solution is to sign Pep Guardiola or Ancelotti, because if they failed to bring Manchester United glory, the fans will blame the players instead of the managers, so they can survive and build Manchester United for many seasons.