Jackman's joke of a score for G.I. Joe is just another in a long list of examples of the downfall of the orchestral score. Gone are the days when every Sci-Fi, Fantasy & Action/Adventure film came accompanied with grand orchestral score by names such as Goldsmith, Williams, Horner, Silvestri & Arnold, replaced by unlistenable noise. These modern "composers" couldn't write an orchestral score if their life depended on it. I sincerely hope this trend dies a quick death.
I wouldn't say, that Jackman is incapable of writing an orchestral score. There's a lot more involved in working in film, than one's capabilities .
As much as I love the 80s sci-fi orchestral sound I think it's good to move to a newer sound and try different things. Also, a lot of the cheaper 80s films tended to emulate the Goldsmith, Horner and Williams approach to a point where it becomes just as obnoxious as todays trend of emulating Remote Control. Although, here and there, you can find a lot of guilty pleasures - both old and new.