For the right return a guy like KJ should absolutely be on the market, but then again who will pay the right return when he just had 20 points in 70 games or whatever? He should have double that next year even if he was still disappointing and 55-75 points if he more or less gets back to what you'd expect out of him based on 24-25 and who knows what he can do if he actually takes a big step forward. He's at that age.
If they are going to trade him, the time to do so is anytime but now. Basically the only scenario where I see trading him now making sense is if it's as part of package for a sure upgrade who's on a good contract.
Also isn't it entirely realistic to expect improvement from within? Even without engaging crazy day dreamer mode Fantilli could very well be a 40 goal >P/GP player starting next year. Likewise 60-80 points out of KJ would not be ridiculous. Sillinger could become legit where he's not only a useful player with right linemates but becomes the right linemate for others. Can't really bank on any of these things happening but at the same time none of them are outlandish, so some or even all of them could very well happen.
Fantilli is already a good player but if he becomes a rockstar that would really change things without doing anything on the market. KJ should be a lock for 40-55 points next year and he really has the room to make a giant leap, at his age time is still working on his favor and with good training he has a ton of groom for growth physically and a real breakthrough at age 24 would be part the course for a player like him. At this point I feel like he's a tough one to predict, he has been so up and down but at the same time can't count the times we've seen a talented player really put it together at a similar point in their career.
Likewise Monahan should be way better than he was but with him and his injury history I don't want to get my hopes up, he already wasted years of his career playing through stuff and without knowing any details, my fear is last season was more of the same, where he really should've sit out for a month or two and get whatever it was fixed.
Maybe too much optimism in this but then again maybe it's time for some, IMO this team is at a stage where it's more likely they improve just by getting older and more experienced rather than the wheels falling off and everyone wanting out just because.