I think Holland deserves some blame.
As others have mentioned failing to re-tool the defense is a big issue the Wings are facing. Big E never belonged in the top pairing, Kindl hasn't worked out,
One that keeps coming back to haunt us is the center position. Flip didn't work out and his replacement was a player that sat out most of the previous year with a bad injury heading into his 30s. Some might say the injury isn't Holland's fault, but he should have a good idea of how injured a guy is before signing them to a multiyear deal for such an important position. As #1 center position goes now it seems like all hope is in Larkin taking that spot.
A big issue I have with Holland is always going after aging veterans come the trade deadline. I think those moves are fine when there are not other big glaring holes that need to be filled. Save the picks and prospects you use acquiring aging players for players we can use for years to come. Sure those moves might have helped us get into the playoffs, but barley making it into the playoffs seems to be a dangerous game.
It's like we are in the same position Calgary was in years ago. Might be good enough to make the playoffs but not good enough to go on that lengthy run. Instead of missing the playoffs to get a better first round pick, they wasted draft picks trying to maintain their playoff position. Being a bubble team for so long is a bad position to be at.