You are completely misrepresenting what @Mil-ing Aroundis saying.
He is saying that the players won’t see Slot as a world class manager or really exciting appointment. Which is obviously completely true. He doesn’t have any experience of winning top European leagues or European trophies.
Therefore he’s going to have to do a fair bit of work in getting the players on board. Reports are that he’s a really good communicator and players love him, so fingers crossed.
For those players with one year left on their contract though the club does not have time for the players to get on board. The contracts need sorting now.
A more sexy managerial (head coach) appointment, e.g. Alonso, Guardiola, Southgate, and the players would have been more likely to sign up straight away as they would have more knowledge, trust and excitement at working with the new man.