The bolded is only true if we don't have a great plan for the excess cap space.
And we don't. The argument is never that we need to trade Marner to execute a realistic plan where we increase the overall impact from that cap space by doing X, Y, and Z. And even in that scenario, Marner should be the 2nd last place we should go to open up that cap space. The argument is always that we lost in the playoffs in the past, so purge anything that looks remotely familiar, even if they're the best parts of your team and aren't the reason you lost, and we'll figure out the rest later. That's not a great plan.
For example, we probably can't afford to lock up Knies long term
We can afford to lock up Knies long-term. He shouldn't be too expensive, and we've had cap hits in the range he'd fall in, even without the rapidly rising cap we'll have now.
I feel pretty comfortable saying they've been passed by NYR, Carolina, Florida, VGK, Colorado, Dallas. All teams that have finished bottom 10 in the league during the Matthews/Marner/Nylander era.
Vegas hasn't finished bottom 10, and is below us in the standings FYI.
I'm also not sure why you think it matters that they've finished bottom 10 in a season in the past 8 years anyway. Most of the league has.
Some of these teams peaking have slightly surpassed what we've been able to do in our worst year in almost half a decade, but I'm not sure what you think that proves.
The core players are top tier players, I am not arguing that. The issue is they are overpaid relative to their peers which has forced the Leafs to underspend on the rest of the team.
They're not overpaid relative to their peers, or their impact, and we have still have enough to effectively fill out the rest of the team.
In a league where 23 minute per night defenseman go for 7.5M, having 22.5M invested in 2 wingers is inefficient. (7.5x3=22.5).
The defensemen that play 23 minutes per night have a very wide range of cap hits and impacts.
Investing a certain amount of money into players that bring that amount of impact and more is not inefficient.