I can't argue with your overall thinking, esp. considering the window is when you've got Matthews/Marner/Nylander here, but where we differ is my opinion that Dubas should not mortgage more of this team's future "going for it" when this team has not proven they are a contender, and their play this year (inconsistent, blown leads, a very shaky blueline) and considering what the path looks like his year (Florida, TB, Boston, for starters).
Basically, I have seen nothing from this team to suggest they are going to have any more success than the past 5 versions, regardless of who they bring in at this point. So I don't want to see another first and another top prospect (of which the Leafs have about 3) gone and potentially be out of the playoff picture entirely in a few years if any stars go and there's no young talent to replace them.
Of course, I'm not Dubas nor am I a Leafs player and I'm sure they disagree but going all in - if not for one playoff, cumulatively over a few years - is when you believe in the team and you see a path. Otherwise it's desperation to appease the boss and/or the fans. To me, it's the latter.
Resist the temptation on the big names and instead bring a depth, veteran 3rd-pairing level (RD preferred) at modest price. In truth, the Leafs could use at least a couple but at some point you have to give the young guys (namely Sandin and Liljegren) some playoff exposure so they can grow from it.
The quoted line, I dispute that: They have been trying to win it every year - consider players like Freddie, Hyman, JVR as own rentals + the trades.