I've been saying for a few years now that the Leafs would be better without JVR and Gardiner, despite their offensive production because of their defensive shortcomings. Addition by subtraction.
The narrative that Gardiner "had a bad game 7" and is vilified for that but is otherwise a steady blue liner is absolute nonsense.
He has a ten cent head, has always had a ten cent head, plays a soft game and is prone to idiotic decisions on an alarmingly regular basis and moreso than any other player I've seen in recent years set up his teammates to be hit or stripped of the puck by making suicide passes at a high rate. He's also prone to a maddening hiccup where he chips the puck away in his own zone, essentially making a four foot pass to nobody at all, simply turning the puck over to open ice.
The production lost by trading Gardiner is, first of all, not needed in the first place, but any half-way decent puck moving defensemen logging the minutes that Gardiner got with the offensive weapons the Maple Leafs have would be able to rack up 40+ points pretty damn easily, so I don't think losing the production of Gardiner is any issue whatsoever. However, getting a more capable defensive player - and that really wouldn't be too difficult to find - would make the Leafs a better team and make them tougher to play against.
I have said for a few years now that the Leafs will never win anything with Jake Gardiner playing the kind of minutes he does. They would be wise to flip him now and get something - anything - rather than fizzle out in the playoffs and watch him walk away for nothing.