Buying a lot of new players does not mean becoming better, ten Hag did it before, in the previous off-season they also bought a lot of new players, but despite this they had an even worse season. New players need time to adapt, to play with the team, all this takes time, and competitors will get ahead. I think that nothing will change for Manchester United, their main goal at the end of the season will be to get into the top 4, but this may not be easy, because there are teams that are progressing better like Aston Villa, which you mentioned, and Tottenham, Newcastle and Manchester United will fight for the Europa League, that's what I think.
Everything works and to hand. If a team is buying new players without tactics and a good head coach, they will hardly see the team's improvement because, in the end, the new players will adopt the team's patterns of playing. But with a good head coach, bringing new players always adds value to the team. If they always want improvement, they will surely bring in new players to help strengthen the performance of the team. If any team refuses to add more new players every season, they will hardly see improvement because, no matter what, every season a good head coach must discover the weak players in the team. So, they need to replace them in the team to not drop the value and performance of the team.
As for me, the only teams I can predict their performance for now are Manchester City and Arsenal. With the set of players these two have and the way I see their players even playing in this preseason, there is a higher probability that these two teams will be the fighters for next season's Premier League. From observation of other teams, I can't really say much about their performances because I believe with the players they also have, they will come along the line and fight for the trophy. Aston Villa surprised us last season with their great performances, so next season we are also expecting a new surprise from another team again.