When Toronto drafted Matthews they already had Kadri, JvR, Bozak and Rielly as established top half of the lineup veterans. That allowed them to hit the ground running when Matthews, Marner and Nylander joined the team. As a result they never had another lottery pick.
Grier wisely dumped our version of Kadri, JvR, Bozak and Rielly which means that even if Celebrini and Smith make an instant impact comparable to Matthews and Marner, there's no chance it improves the team enough to escape lottery territory. We simply don't have the infrastructure around them. This is a completely different situation than the Leafs were in.