The objective of a trade is to make the team better, both short term and long term. IMO, this deal would make the Leafs better as they'd now have one of the best defenses in the NHL (Reilly-Pietrangelo; Muzzin-Pesce, Sandin-Dermott, Holl, Lilijgren), and would still have a dynamic offense losing Marner but adding Svech.
Canes OTOH, end up with a much weaker defense (and even worse if Hamilton goes UFA where they'll end up with no top 4 RHD), are even softer than they were when Boston ran over them in the playoffs, and are now imbalanced in terms of goal scorers vs. assist guys.
I realize this deal wouldn't have any chance of happening, but IMO, it wouldn't make Carolina better, short term or long.