I don't have a problem with that personnel. Jarnkrok is a big risk, but assuming he reverts back to 2020-21 form, there is not much to dislike. There are 5 high end (4 elite), play limiting players, that don't need to be sheltered. Engvall, Jarnkrok, Kubel and Robertson all have 10-15+ goal potential too.
The problems are Kerfoot sucks balls as a top 6er, and if a Simmonds or Clifford pushes Robertson out.
I also think Keefe is a bigger issue. IMO they need to open things up a little bit. Matthews and Marner will wreak havoc no matter what you ask them to do, but even Tavares and Nylander's offensive impact was neutered last year (particularly Nylander). They were bottom 5 in the league in rush chances generated. I think you have to have a bit of the quick strike element in your game. Especially in the playoffs where everything is so tight in front of the net. The Leafs can skate circles around the ozone all game, but its hard getting pucks through. Especially with the depth of talent on D. They have the luxury of being able to cover any mistakes.
Last year they were actually a much better team trailing than when the game was tied:
Tied 1330:52
xGF/60: 2.74 (5th)
xGA/60: 2.34 (11th)
xGF%: 53.99 (7th)
Trailing 1021:08
xGF/60: 3.03 (2nd)
xGA/60: 2.29 (3rd)
xGF%: 56.59 (1st)
Nylander Tied 376:19
xGF/60: 2.88
xGA/60: 2.46
xGF%: 54.00
Tavares Tied 369:01
xGF/60: 2.56
xGA/60: 2.48
xGF%: 50.83
Nylander Trailing 307:04
xGF/60: 3.30
xGA/60: 2.37
xGF%: 58.20
Tavares Trailing 295:33
xGF/60: 3.21
xGA/60: 2.52
xGF%: 56.01
Some of that is obviously the leading team sits back. But the D actually improved when they turned it up down in games. Thats not the case for most teams in those situations (e.g. Boston from 1.94 xGA/60 to 2.04, Carolina 2.2 to 2.6, Calgary 2.14 to 2.6, Minnesota 2.15 to 2.15)
Just loosen things up and create some more offense from the bottom 3 lines off the rush, to generate cleaner looks. I know they want to possess the puck, but they do that even more when they push the pace a bit.