p-bass pickups and Rics
I remember a time when there were no aftermarket pickups! The choices were slim. I even wrote to Seymour Duncan, back when he had a pickup rewinding service (before he had a zillion pickup models) about having them rewound a bit hotter, and he said they were "limited in design" and wanted to make me some new pickups (which I guess is now his Rick replacements) or he could wind them about 50% hotter.
When I bought a P-bass pickup to put in my Rick, it was about the only replacement pickup you could buy (and I suppose J pickups). Later I bought an old style Carvin humbucker (a kind they stopped making a long tme ago).
Then of course DiMarzio came out, and everyone was using their pickups in Fenders.
As far as not being able to improve on stock pickups... I think the DiMarzio Model P was a better sounding P than the stock units, and the J's were humbucking, which to me is an improvement also.
And obviously when RIC decided to come out with some "modern" pickups (the humbuckers) they built a new bass around them! Which was pretty much what I was trying to do modding my bass.
Even the Hi Gains show that they think the old single coil pickup designs needed improving.
I appreciate the original designs now, because they are old, but I like modern basses too. For example, I couldn't see playing one all the time, but I'd love to have an EB-3.