You're forgetting that they'll be getting better in 3 years, when all their new contracts are going to be active. They'll also have enough cap space to fill in replacements.
They could grab a big defender that you've always wanted!
The Leafs best window to compete for the Cup is this year and next while Leafs 3 Amigo's are on entry level contracts paying them < $1 mil each.
Sure the kids will improve but not exponentially at a level to absorb the losses of veterans that must go for Cap reasons.
Case in point Mathews is a 40 goal man now making <$1 mil ELC and just because you increase his cap hit 10X up to $10 mil you don't get his 40 goals to improve by 10X ie 40 X 10 = 400 goals now that he is occupying so much more cap.
Also true for Nylander who say goes from <$1 mil to $6 mil per... That means in order to afford Willy next year they have to let 30 goal & 60 point JVR ($4.25 mil) walk away. Willie gets marginally better and going from 20 goal 60 point now (to say 25 goals and 75 points) but its not going to 50 goals 120 point player (when adding Nylander and JVR production together) to absorb the loss.
Willie at 20 goal + 40 assists 60 points + JVR at 30 goals + 30 assists 60 points = 50 goals & 120 points total this season
>>>>>> improved Nylander 25 goals and 75 points next year and JVR (done due to UFA) replaced by Marlie next year,
for the same cap hit.