Any shoe can cause an injury if it is not fitted or faulty, old or new, or you are wearing them when you hurt yourself.
Everyone values something different, the usual compromise is court feel for cushion. Retros usually have more cushion, new shoes often have less cushion and more court feel, however some have firmer vs softer cushion they all differ.
After Agent zero wore dolce and gabanas in an NBA game and Thabo Sefalosha wore air max trainers (i think) it really comes down to preference.
Lot's of players slip all the time, it is a court issue not a shoe issue in the nbl (In my opinion)
Should he wear new shoes, no. He should wear what ever makes him comfortable.
I have been contemplating Harden 1's or Lillard 3's, but will probably get the NIke air zoom generation (Lebron 1's) when they re-release. Why I went undefeated in them in high school and love the shoe, will they be the most comfortable? I don't jump high enough for it to matter anymore!