In the premier league today, signing players don't guarantee excellent performances - Chelsea had some of the best players in Europe last season but barely any result to show for it. Every piece of the team matters same way a tree can't make a forest. I have high hopes for Pochettino. We'd know in the next couple of weeks when the PL is in full swing.
There is an expression that order beats class and even with the best players you will not be able to win titles if you do not balance the squad. That is, the conditional stars should have players who will take on the rough work so that the stars are engaged in creativity. I don't quite agree that Pochettino's work will necessarily be visible in a few weeks. Balancing the composition may take half a season and even a season in general, let's recall the example of Arteta. The most important thing is that the club management has patience and trusts the coach.