JD was a major part of the Johansen fiasco and couldn't convince Panarin to stay while he was here. If Jarmo is the reason why players have left the team, then having a well-respected hockey guy like John Davidson above him doesn't seem to make a difference.
McConnell has authorized spending to and above the cap. He's willing to provide the funding needed to assemble a winning team. Not sure what more the fans could want from him.
IMO, this comes down to two major things:
1. Players choosing to leave despite being on a playoff caliber team and being offered fair value. Maybe the team could have retained a few guys if they'd been willing to overpay, but overpayment of players - particularly young ones - has conventionally been seen as a quick and extremely expensive way to run your team into the ground. Teams bypassing the salary cap wasn't really foreseeable and is expected to change as evidenced by Jarmo's insistence that other teams will be in tough situations this offseason and it may be the the Jackets' benefit. Whether that comes true or not, I have my doubts. But Jarmo clearly believes that teams can't get by if they don't manage their cap very tightly.
2. Drafting and development. 1st rounders under Jarmo have been Wennberg, Rychel, Dano, Milano, Werenski, Carlsson, PLD, Foudy, and Chinakov. Outside of Werenski and PLD, there's absolutely nothing to write home about. Further, Jarmo misidentified Wennberg's qualities and may turn out to be wrong about a number of others (Texier, Bemstrom, etc.). Part of that is bad luck in terms of draft position (all of them are outside the top-10 besides Werenski and PLD) but I would still expect there to be more success at the top end of the draft than Jarmo has produced.
As for development, I think something is clearly amiss in regards to the forward ranks. Great things can be said about the team's ability to develop goalies (due in no small part to Manny Legace) and on defense (presumably that's Brad Shaw) but at forward guys have just not done well. That means guys failing to develop into NHL players (Milano, Rychel, Bemstrom) and more established guys failing to take the next step (Josh Anderson, William Karlsson).