In several versions of an interview,
J. Michael Straczynski
said he received this slogan in an e-mail from either FermiLab
(supposedly posted on a bulletin board there).
I'm not sure whether he remembered it differently at different times or if one of the interviewers was sloppy.
Anyway, what does it mean? Here are two possibilities that occur to me:
(1) Star Trek is a bit more idealized and Babylon 5 is more gritty, 'realistic', what have you.
(2) Star Trek mostly has to wrap up plot lines in a single episode, whereas Babylon 5 had 5 years to work out consequences and implications of choices made by the characters.
So the way I read this is that 'real-world' problems need deeper solutions than the writers of Star Trek could fit in. (I like both shows, but I distinguish them from 'reality'!).
Case in point: And the Rock Cried Out, No Hiding Place.