Manchester United were good last season under the new coach, this season they will be better. It is two straight wins for the team now in the pre season games, and although these games are not the perfect games to judge how the team will perform next season, it is a good test that can show the direction of the teams progress and the progress of every player in the team under the manager. Some more players will join Manchester United, Onana the goalkeeper is almost a done deal for them, they will be strong in goal, defense, midfield and attack, they have the players and more are coming.
Why do you think United will get better? I am a United fan myself, but I think it will be difficult even to keep the third place, and even more difficult to climb higher. Buying Mount is good, buying Onana is just a replacement for De Gea. I don't see any major enhancements. If United got Kane or Osimhen, you could say that they are getting stronger, but in my opinion now +- the same level.
Regarding the prematch for Manchester United, that in the last season also Manchester United got good results. Also, the good results in the prematch last season at least still continue to occur in the early matches of Manchester United in the Premier League. But unfortunately, again and again Manchester United still cannot play more consistently and yes, if Onana will really play at Manchester United next season. Then, maybe Onana can consistently to make clean sheet results and of course it will be good, and even though your consideration is only replacing De Gea position. But, if Onana can play better it will make Manchester United difficult to concede also by the opposing team and it will be a good defense of course.