Adam Herman at Blueshirt Banter broke this down in significantly more detail than I can, and you should 100% check out his post here.
When you think of a rebuild, you immediately think of prospects, developing those prospects, and putting these prospects in a position to succeed. It’s the only way a rebuild works. Sure, the elite level players don’t necessarily need a whole lot of grooming, but that’s a small percentage of the players that make a rebuild successful. Development is key.
The majority of players will need at least a full season in the AHL before they get brought up to the NHL.