How to change Alt + [ and Alt + ] shortcut?

You can install a script to select the next or previous layer, and then assign a custom keyboard shortcut to the scripts. You would still be stuck with the original keyboard shortcuts though, as there is no way to disable or reassign them. An added bonus is that such a script could also select hidden/invisible layers if required and not skip over them.

Alt+] shortcut is an invalid shortcut. You have to add Control to that or an F key. The shortcut Alt+Control+] will work. It might be assigned already but it will tell you if there is a conflict. Photoshop will tell you where to go to resolve the conflict or just accept the change. Just find the menu item you want from the dropdown list and click next to it in the box to type. It's really pretty easy, Photoshop will prompt you what to do.