Bringing in new players does not guarantee that next season a team's performance will immediately improve, but what must be realized is that it is a step that must be taken for other possibilities, the top Premier League teams have prepared to improve their strength to cover next season and of course no one knows for sure what will happen but at least there will be changes that occur when a team makes changes.
Having new players in the team does not guarantee that a team's performance can immediately improve because most players also need to adapt to a new atmosphere where the team will also see a new atmosphere with players who are different from before. But this can also have other effects as you said where the team must try these steps in order to have the potential expected in the next season. Because when the team does not buy new players when there is an opportunity and ability, the team's condition will not change in a different direction.
I agree with that and maybe we can take the example of Manchester City, they recruited players in the middle of last season and at the end of this season they continued to recruit new players, but unfortunately the steps and efforts they made did not get satisfactory results. They failed to get a single trophy this season, and most recently had to be eliminated in the last 16 of the WWC by Al Hilal.
However, if the club is more careful in recruiting players, this can really change the depth of the squad and make the team perform significantly better on the field.