Well, what was professional then seems amateur now, but some of the JG products had some useful and even inspiring content. I am sure the number just of new MgT products sold probably outpace the number of JG resales by well more than two if not three orders of magnitude, not even considering the price differentials. I am also sure that for content and ideas, the bang for the buck in the old JG stuff is therefore relatively better.
It is still relevant for the GM looking for inspiration and content rather than a complete, narrowly-defined, straight-jacketed into an overdeveloped minutely-detailed "one-size-fits-all" master "only this exact setting exists" turn-key product to which nothing needs to be or can be added.