Even if Nylander stayed at a 60-70 point player, that is good enough for your 3rd best offensive weapon.
It is better to add diversity and versatility to the roster.
You surround Matthews, Marner, and a 60-70 point Nylander with a couple of Hymans plus a top 4 defensemen, then you have more depth and more different types of players.
The teams that win the Stanley Cup are teams that can win in many different ways other than just trying to outscore their opponents.
Dubas thought that Tavares, Matthews, Marner, and Nylander were this generation's Gretzky-Messier-Kurri-Anderson or Lemieux-Francis-Jagr-Stevens.
He was very mistaken.