For a long time, I kind of got it. I was not a slap fan. I never found slap bass players to really be super inspiring... Larry Graham did good. But Flea, Marcus Miller, Stanley Clarke, etc... all these guys just didn't really do it for me. But then I witnessed this live clip from 1979 by Casiopea, featuring Tetsuo Sakurai on slap bass:
I don't know what it is, but just how rock-solid his tone and playing are pretty much everything I would ever want out of slap bass. The fact that he slapped for this entire tune and never once sounded thin or weak in the mix amazes me. And he knows when to hold back and groove, and he knows when to let loose.
I've heard he's not considered anything particularly special in slap bass circles, but for me he's pretty much the slap bass player I would want to sound like. Plus, because this was Japan in the 1970s the entire band sorta looks like they're dressed as my grandpa, but Sakurai still looks so cool.