Yes, while Danton is a highly-skilled player, there are simply too many forwards on the NHL roster and salaries need to be moved too. Between Kuraly (whom hasn't played too well so far this season,) Vatrano, Beleskey & Spooner - there simply isn't enough space.
Heinen, Czarnik, Cehlarik, Agostino & JFK are all players whom could benefit from, and are ready for the NHL. If you want to say Agostino & Czarnik are fringe-players I'm ok with that assement. However, there simply aren't enough spots right now to hold everyone, and the cap-crunching has begun from Sweeney.
Heinen is a top-6 forward in my opinion, and he needs to be in the NHL. It is rather unfortunate that players like Beleskey and Vatrano aren't providing anything to the team because Heinen can, and already has.
Something that I don't want to happen but I know is a real possibility - Sweeney will explore a trade route that involves Heinen, Cehlarik, Czarnik or a combination of them to acquire an impact NHL player.