Who are these young defensemen that Keefe was supposed to have developed since 2020? Liljegren? Well, we've seen Timothy develop quite a bit since he first entered the league 133 games ago, though he is going through a rough stretch right now. Sandin? 140 games as a Leaf. Dermott? 250 games as a Leaf, but only around 120 games available to him when Keefe was coach of the Leafs. Or is it Timmins with 22 games as a Leaf? These young D haven't cracked 200 games played with the Leafs, but I'd argue each (perhaps not Dermott?) has developed into a better player than when they arrived, and because of age, skill sets, and the number of games they still have to play will continue to get better.
Defensemen take a long time to grow into the player their abilities allow them to be. Lily has had some great games since he's been here. I've been a huge fan since he started to break out last year. I'm still a huge fan. Will he contribute come these playoffs? I certainly think so. But, Keefe is - I think - using all the the time he has to find out how he can use the players he has at his disposal. IMO, as he should, because he is the coach of the team, not just a young defenseman. One of the assistant coaches, Carbury/Chynoweth/Malhotra/Muzzin can massage the ego of a player, boost their confidence etc. Keefe's job is to find out what he has, who can succeed with whom, in what situations, and ice the best team he can.
I'd suggest he's doing the same thing with the F group, anticipating the return of ROR, and mixing and matching until that return to evaluate what our best options are when Ryan returns.