No argument there, it makes a gigantic difference. Fans focus way too much on the players quality instead of their profile. I think with the exception of Barcelona because of Messi, Real Madrid and maybe PSG, the other top clubs have very equal level of top quality players. Maybe some are slightly better than others but certainly not a decisive difference. Profile of players and how incorporated they are within the team becomes more of an influential factor as a consequence of this relative equality.
Having said that, Mourinho has very little if any history of having a clear vision of how he wants his teams to play. In fact that's one of the pluses about him according to his fans which is an argument not without merit. The other side of this potential advantage is he is hired almost exclusively to win trophies using every trick in the book to navigate each test. You don't hire him if you have a specific vision of how you want to play because he's never shown a particular commitment to that. So in a way, the man has already done what he came here for, he relatively stabilised us, won us a couple of trophies which whereas they do not indicate high quality, are still great memories and help the status of the club, and got us on course to reaching 80+ points in the PL. Unfortunately for him, his approach will always have a lower ceiling and will need others to not be at their best.
Just to add from last night.
In the first point, we definitely agree. People pay too much attention to individual ability or quality of players instead of their profile or how they fit in a team system. For instance, there is a reason why Salah looks like a world-class player in Klopp system, or many of their attackers like Mane last season. Because they're exactly the kind of players that fit the profile for their attack. Put another system or manager there and they will not be half effective as they are.
On the other hand, there is no doubt that Liverpool system does a disservice to their defenders and make them look worse than they are.
I used Liverpool as an example but you can choose many other teams such as Napoli, Atletico, Chelsea, City and so on. The quality of system and profile of the players in it is what makes more of a difference nowadays and that's the reason why buying for the sake of buying won't get you anywhere.
Yes, you could hit a jackpot and get yourself a player like Messi but you could argue that even Barcelona system is the one that really elevated Messi to the status he has, looking how he functions in Argentina team.
As for the second point, there we definitely don't agree. To be more honest, I hope Jose isn't past it and has the patience to build some of his teams from the past. Mourinho does have a specific vision of how he wants his team to play. His approach also doesn't have a lower ceiling and isn't in need for others to not be at their best. You can't win EPL twice in a row and still hold records with most home wins (2005/06), most away wins (2004/05), along with a record most points without a clear vision of the way your team play. If that's ancient history, you don't win La Liga against one of the best teams in world history with record points and goals, but no clear vision.
What's also evident is that both of those teams played in a similar manner. A highly productive counter-attacking team who's efficiency depends on a quick transition, creating width and stretching the defence on the counter or not with a highly mobile striker on top who is good on crosses.
Now, it's perfectly clear that he is trying to make such a team in United. In attacking sense, Leicester away was a pretty much very good example of his playing style and the way he attacks.
Whether will he take us there or not is another question and I have my own worries about his patience when things aren't going his way. But, to say this particular team is an example of a Mourinho one and his vision is pretty much wrong. It's a work in progress at this stage.