I have said my 2 cents on this in the past. It is not that they can't win without Nuke but more that they can't win without both Nuke AND Landy out of the lineup at the same time. They need at least one of those two in the lineup. Without both of them the top-6 become weak defensively, weak in winning battles in the corner, weak in cycling the puck and especially weak in front of the net in both areas of screening the goalie on shots and tipping shots. They don't have anybody in the system that can bring those skills/qualities to fill in. Obviously it is very hard to have one player in the system/lower lines that can fill all those gaps in the top-6. The player doesn't need to fill all the gaps but you need somebody to fill most of them. The Avs don't have that anywhere in their system currently.
Yeah they can win without Val, but they need a healthy Gabe, playing at close to the level he was at before. Probably Lehky too. They need two guys like that who can play in the top 6. Wood and LOC can play a similar role, but you don't really want them in the top 6.
I've always thought the plan was to let Val come back this year, because their options were so limited, and then hope he can put in a clean full season, which could allow them to trade him at a fair value next off season, and shed much needed cap space.