Call me crazy, but Seattle isn't going to let Adam Larsson, no matter how good he's been for them, get in the way of acquiring Mitch Marner, if indeed Marner is willing to go there, etc.
Your assertion that the Leafs need to get something that helps them both now and in the future is correct, but with the 3 pieces you've laid out, are missing the "meaningful" or "positive" contributions. These guys literally "check boxes", without any consideration of whether a team like Toronto would even want them, even if it was free.
Burakovsky is a cap dump at this point, and likely holds negative value. If the Leafs are looking to spend $5.5m on a winger, they would be better off simply re-signing Tyler Bertuzzi.
I don't think they'd have Larsson on the table whatsoever. He's a part of their leadership core and he's a type of player who is fairly limited in today's NHL. He's helped unlock a high-end part of Vince Dunn's game and the result has been a reliable top pairing right out of the gate. A flashy player won't convince them to move away from that. Doubtful that Larsson would want the move also.
I'm not sure what you mean by "meaningful" or "positive" contributions. I think what you mean to say is established elite, and my argument is suggesting that isn't the best use of Marner as a tradeable asset, because those trades end up being closer to one-for-one and the majority of those established elite players will generally eat up the majority of that cap.
Burakovsky comes in and puts up Bertuzzi's numbers this season, Shane Wright plays a rookie season mostly in Toronto's middle six looking like a responsible two-way guy, 30 points out of the gate and Nelson starts his pro career off on the right foot... Are the Leafs any worse off knowing that the other $6m in cap flexibility is being used to bring in a significant piece on D?
That is how the Leafs increase their available depth. Marner's outgoing contract would facilitate the addition of three active roster players--two forwards in their top nine and whoever the other ~$6m would go towards.
Shane Wright is a guy who's development has nearly flat-lined since the draft 2 years ago. That's a massive red flag for a player's long term upside, and he looks a lot more like a future Alexandre Daigle than Patrice Bergeron. Toronto has Fraser Minten, who they would probably prefer to get the spot in the lineup.
The prospect you've included, maybe he's appealing, maybe he's not, but he's a prospect... and we have not addressed anythign in terms of meaningful contribution to the Leafs in the now or short term.
If Marner goes, the base, base requirement for any deal is that the Leafs have to get back at least one "top half of the lineup" player with a good contract situation. Can be a right shot defenceman with size, can be a #2 centre, or can be a 50-60 point winger; although I think the winger would be the least desirable of the 3 options.
Burakovsky and Wright do not meet any of those criteria. The Leafs offer for Burakovsky & Wright should probably be Nick Robertson; recognizing that Burakovsky is negative value, and Wright's value is more than Robertson's.... not Mitch Marner.
Shane Wright's 20 year old season this year has calmed a lot of the doubts that he had coming out of the draft. Seattle fans would rightfully hesitate at making this deal because Wright is projecting as a solid middle of the roster two way forward as a projected floor. More hype than any prospect in the Leafs organization currently. And a high ceiling at C where the Leafs may soon have a bit of a depth issue. Still actively playing on a Coachella team with Calder Cup aspirations.
We're on different ends of the spectrum when it comes to valuating these players.
Even Burakovsky. When healthy, he's been on par with Bertuzzi looking at the recent histories of production in these players. The vast difference is the style of play. Burakovsky has the edge in playoff production and overall experience though considering he had two Cup rings at 26.
Like I said before, this trade isn't the flash of a Seth Jones or a Jusse Saros trade. But the return offers the Leafs a longer upward trajectory. And it creates a significant amount of cap flexibility for them moving forwards.