I can't justify firing a GM for overpaying his young stars and bringing in a UFA @ 11M a few years ago. And it's not like Nylander, Matthews, Tavares or Marner have been terrible, they just collectively haven't gotten it done in the playoffs.
This trade deadline was a disaster but almost universally analysts and fans felt this was the year to go all-in, clearly do did the Leafs, so Dubas pretty much did.
After losing in the play-in round last year, Dubas saw his approach needed adjustments and he made them. He brought in toughness, leadership and a very solid signing in Brodie as well as doing a solid job managing a sliver of cap space in the off-season and during the season.
A GM can't tie up his players' skates or set games strategies, he just provides the pieces and the coach and team have to deliver. To put it mildly, they did not.
As for what's next, I said previously, if Dubas internally says he believes in this core and is adamant they stick with them, then he should be fired. The salary cap isn't the problem, depth isn't the problem, the blueline or goaltending isn't the problem, the core is. There really isn't much of a debate over that among us, but it's only what MSLE, Shanahan and Dubas thinks that matters.
Unfortunately, I don't believe for a moment Dubas will do anything drastic like trade Marner or Reilly, in which case the question posed by this thread is likely going to be the same next April.