I can't see how they can really fix things without starting over completely - and they've already said they're not planning to do that. Henry Cavil is going to be back as Superman, etc.
Best bet would probably be to just make good, individual, stand-alone movies (and James Gunn can definitely do that), but that's not what they want either. They want what Marvel has, and if they can't have that then they'll damn well continue to fail trying.
Both James Gunn and Taika Waititi seem stretched pretty thin lately and it has shown in some of the work.
Better James Gunn than almost any other option I can think of though.
