In the case of Al-Nassr, a good coach could fix things well especially that they have enough funds to recruit quality players. I said quality players and not top players because names mean nothing nowadays. Whenever I see PSG success in UEFA Conference League and in the other competitions, I say a good strategy and teamwork are the key to success. Al-Nassr lacks seriously these two points.
I assume you mean PSG's success in the UEFA Champions League and currently the FIFA Club World Cup? The club failed to make any impact in Europe even when they had the best players in the world. Before now, Nasser Al-Khelaifi thought that hiring the biggest or most expensive players in the world would bring success to the French club. But this was not the case and PSG is now successful with average-rated players.
You are right. Most top clubs in the Saudi Professional leagues need the right coaches and dedicated players, and not necessarily big names in football.