You basically do what Florida did and you take a step back for one season.
That's not taking a step backwards for one season. That's taking a significant step backwards for the foreseeable future, and potentially until another full-on rebuild unless Byfield/Clarke/unspecified prospect turns into things that none of them have shown to be.
That's very, very different from what Florida did. Florida exchanged a very flawed player entering his post-prime for another top-tier NHLer in his prime. They did not trade the reigning MVP in his prime for prospects and young players that are struggling to establish themselves in the NHL. Florida's not exactly excelling after that trade anyway, so weird thing to point to.
At the end of the day if the Leafs sign all of Nylander/Matthews/Marner to bloated contracts they are going to be taking up a huge chunk of salary going into their 30s instead of their mid 20s like their current contracts. Having them take up north of 40% of the cap as they decline probably isn't a winning formula, nor has the current formula had success.
At the end of the day, if the Leafs sign all of Matthews/Marner/Nylander to reasonable contracts that you'll incorrectly call bloated, they'll continue to be contenders for the foreseeable future instead of destroying their team for no reason. None of them are starting any kind of serious decline soon, and this formula has shown to work to produce top-tier teams. You don't abandon it when you're finally going to get a rising cap and internal depth coming through.
I didn't touch on the prospects part of your post (sorry). Byfield has been playing on the top line (top competition!) in LA for a month now and has scored 9 points in his last 10. He is far from a sure thing but he has been promising. His underlying numbers are strong as well (27th among F in GAR/60 - minimum 200 mins).
Clarke has been tearing apart the OHL. He is putting up a significantly higher NHLe than Makar was at the same age (52 for Clarke, 39 for Makar). He also isn't a sure thing but his numbers are hard to ignore.
Byfield is a 3rd liner playing at a 6 goal, 40-point pace, at an age when Matthews was already a superstar. You don't trade the reigning MVP for somebody with an alright 10 game stretch.
Clarke is having a good short season in the OHL as a 20 year old, but that's the OHL, not the NHL, where again, Matthews was a superstar at that age.
They are good prospects, but they are likely not going to become anything remotely close to Matthews, even if they become NHLers.
And they don't really fit the timeline you're creating around Tavares and O'Rielly.