I would change it to read that aftermarket pickups will likely make a difference. Whether the difference is for the better depends upon what you are looking (listening?) for. Also, there is the 'wow' and 'brand name' factor that most always influences folks. People ask, "Why should I buy the Epi Slash (using Chinese pickups) for a thousand dollars, when I can buy the '59 with Gibson USA pickups for nine hundred dollars?" Good question. You'd buy it mostly because you like the color, and you don't get the Slash logo with the '59.
FWIW, I was at the Gibson Nashville store wandering through a lot of guitars I couldn't afford. To my old and tired ears, the Epiphone Slash Goldtop pickups sounded fine. I wish they'd make a '59 style Goldtop for a hundred dollars less, though.
People say (and they are no doubt correct) that the cheaper the guitar, the cheaper are the electronics. But cheapness doesn't always mean a lack of sonic goodness. One of my favorite playing and sounding guitars is an ugly, bottom of the barrel Schecter C-6 with their own branded (probably made in China) pickups. I would never change those out. They do what that guitar is supposed to do, and they do it well.
On the other hand, the electronics (switches and pots) on an 2015 Les Paul Standard started to fail after a year. And the pickups were muddy sounding. I replaced them with a matched set up Duncan pickups, along with new wiring harness and switches. Transformed the guitar.
Generally, pickups don't go bad, and with all the hobbyists who like to change things out, you can easily find discounted used sets. It's pretty quick and relatively inexpensive to experiment.
Somewhere on one of his weekly firesides, Phil McKnight offered an opinion--coming from his years of wiring pickups. He said something to the effect that automated machine wiring gives you a consistency you won't get from hand wiring, but the hand wired product tends to be more valuable in the minds of customers since... well, since it requires a human to actually wind the coils. So there's a sense of pride of ownership a customer gets from that, which they probably don't get from a robot made pickup.
