That's just it! You hit the nail on the head. GC deals in a LOT of different brands. The sales people are not going to be experts in all of them. More often than not, I haven't been able to find in expert in a certain area. Even if they say they do, it ends up being someone that blows smoke up my ass, because they end up being flat out wrong.When I wasnt presented with a name or cant remember the sales person I've described the sales persons physical appearance to the person at the cashier and they know whos who.
I've never had a problem with GC really...yeah, a lot of those people dont know a lot about some of the gear (or any huge store like home depot sometimes, walmart...) but its not hard to just look that stuff up on the net, they've always had pretty friendly sales people. When information and independent reviews from the net is so readily available these days for anything and everything I'd much rather deal with a somewhat uninformed sales person who's friendly than some know it all douchebag you get a lot of times in small pricier types of stores (like bike shops for example!).
Do your own research before going into GC. You have to know what you want walking in there. It's not a niche guitar shop that specializes in one or two brands.