Can I save these bathroom walls?

I’m tackling a DIY renovation of my bathroom. I’m gonna replace everything (tub, fixtures, vanity, mirror, etc). I cut out some of the wall and got the tub removed. There’s some minor mildew and mold when I pulled out the wall but I can fix that easily.

The issue I have is that the previous owner had one of those plastic/fiberglass shower surroundings that was merely glued to the wall and he also had some board trim glued to the wall also. I tried to remove it as carefully as I can but the outer paper of the drywall(?) peeled off with the trim and surrounding exposing that internal gypsum(?)/crumbling thing inside.

Can these walls be saved? Is there any way I can smooth them out so I can repaint them or lay tile when I’m ready to finish?

I was thinking of using joint compound to cover all that exposed area and the glue but I’m open to any suggestion. Here’s some pictures below to see what I’m talking about.