A lot is made of the fact that Roddenberry signed off on FJ's work, but it's well known GR didn't mind making a buck when he could and short changing others, in this case the fans. To him FJ's work was a good merchandising opportunity, and it was so far as it went, but the fact the work was quite inaccurate in many respects. If Matt Jefferies had been/remained involved the inaccuracies would likely have been less numerous. And back then accuracy for this kind of material wasn't seen as important as it is today (and today we still get inaccuracies although they might not be as immediately noticeable).
Lets be clear. To criticize FJ's work is not an indictment to devalue it. It's fair commentary without taking away any credit to FJ or any significance of what it meant to fans at the time. As has been said upthread it is an important and significant work in terms of Trek merchandising, indeed in genre material merchandising overall.