I'm disappointed: I was really expecting someone to argue, I put a Seymour Duncan JB clone in mine and got a huge improvement in sound through my 10w SS jar 'o' angry wasps... 😆
My JS is stock and the only thing I'd change is the fingerboard radius, which has never really suited me. I've got better guitars and wouldn't waste the money on more expensive pickups. The stock single coil is decent enough quality and to my ears the 'bucker matches it adequately when both are working together. Of course it's going to sound weak if you stick to the piddly 9 gauge strings the guitar was supplied with...