Why? Just because of the big names? You clearly have no idea how they performed at Ajax.
Stam showed very little tactical intelligence at Jong (Young) Ajax. Constantly selecting players with no future at Ajax (chance of reaching the 1st team) instead of the real talented ones.
Bergkamp is known for being silent. Sure he will have influence on individuals (just like Stam has for defenders), but their value for Ajax has been nothing compared to Frank de Boer.
I'd like to describe De Boer as very authentic in huge contrast with all the crazy behaving actors out there. No nonsense, honest, modest, calm and realistic in interviews but very driven and demanding (a true winner) and very normal. There are stories from people who were surprised by seeing him helping his wife out with her (furniture) store in his rare spare time. It must be a funny surpise to see Frank de Boer delivering some stuff at your house.
Although most non Ajax supporters hate Ajax (jealousy i guess), almost no-one dislikes De Boer. Despite or maybe because his indepedent acting. Never saying crazy things in the press, never playing a role. Wearing his frown if not satisfied but not complaining, and despite his sloppy word choice contentwise alway saying the right thing (socially intelligent).
In a very difficult time at Ajax (if you know the club, you know how difficult it can be working there), with the whole club fighting and a lot of negative press, he managed to keep his team out of it all, kept calm and won 4 titles in a row. While many people thought PSV had the better team. Every year building a new team, without complaint and making it work with not the best material (because Ajax did not want to spend big money anymore). That's a big achievement.
Negative point is that many Ajax fans thought the team played too boring (and i agree). But Ajax is known for the very critical and spoiled fans: winning is not enough.
If he'll come to Everton, he will bring Orlando Trustfull with him.