Seems like I have this conversation about once a week offline.
The conventional wisdom about Bartolini has always been a headscratcher. In my reality, here's a sampling of the basses I gig with...
All Bartolini installs. Not a polite one in the bunch. If I try I can make some of them sound muddy, intentionally but the clear, full open sound is only a technique change away. No highs? LOL. Look at a Malcolm Hall Brubaker video and get back to me. And he typically keeps his treble flat and simply pulls back the mids.
IME Bartolini pickups predominantly sound like what you put them in, notwithstanding a strongly voiced onboard preamp. They are not magic. I have a lot of basses that sound great unplugged. They sound like that only louder when plugged in. They have Bartolini electronics.
IME most people dial back the volume on their bass because it seems it makes it easier for them to control. IF they want more high end they simply crank the treble up. Yes, I know that would seem like the thing to do but it usually isn't. They typically have no idea what that does to their sound and point fingers at what they think might be causing a shortcoming when the problem is actually them. How many times do people actually ask " What could "I" be doing wrong?".
It's fun to hand an "I don't care for Bartolinis" person one of my basses and see the bewilderment. They don't sound like they "heard" they would. And most of my basses have off the shelf Bartolinis, not custom wound. I know people want to believe there's something special but there ain't.
Bartolinis let a good to great bass sound like it sounds... like a great mic handed to a competent vocalist. They'll help amplify a dead instrument but they aren't magic... though in the right bass in the right hands they can sound that way.
Maybe they simply sound better? Because in actuality they don't have a sound!