I had partial delamination on my Fleetwood and it is repairable if you can fold the outer sheet out and plywood behind is not badly rotten.
Using liquid nails, you zigzag the glue on the panels and press it back.
Pressing is tricky as you need to push big surface.
I had my camper park between house and masonry fence on other side, what gave me good support for pushing sticks. Used 2x12 planks to push as blocks for flat surfaces.
So if you avoid new siding purchase, the repair can be done in less than $100 material cost.