This is a possibility, that is just hitting me and part of me feels like this is in too much bad faith to even consider but it also makes sense in a way i cant get out of my head.

That Izzy's death was basically the writers' way of dealing with Ed's lack of accountability and growth this season.

That what they mean by Ed can let go of Blackbeard now is that the crew/audience can let go of the things Ed did as Blackbeard/Kraken and move on now because the Blackbeard part of Ed has died with Izzy. There will be no further reflection of this. Ed gets to walk away from that now and find peace and we, the audience don't get to question what happened to all the issues he was dealing with.

Izzy is Ed's version of Frenchie's box in the flesh and apparently the message of this season is lock it in the box and move on.

Ed's lack of growth and the point of Izzy's death were never two different problems. It was the cause-effect of the same problem.