I am hoping for a continual positive outlook in this and future Jeff Berlin threads, and by this I mostly mean the people responding to Jeff. He has his specific point of view, as a teacher should. If you feel you can benefit from it, then Jeff's a great guy to learn from. If you are not really interested in being a proficient player to a pro or near-pro level, then certainly, plunking around is a fine way to spend some time and maybe be ready to play some classic rock at your local bar. Nothing wrong with that; it's an enjoyable hobby and pastime. IMO Jeff is addressing his approach to those who want to be more. It is my experience that, because bass is one of the easier instruments to learn to play SOMETHING on-- you don't have to go to Berklee to learn to hammer the root with eighth notes-- a lot of pedestrian folks think they don't need to learn anything more.
Some things you'll learn by experience -- feel, time, stage presence-- and maybe with a little discussion off the stage on these elements. Really learning music-- the way a proficient pianist might, for example-- takes time and work. I can't claim to be the world's greatest bass player, but I do aspire to be, and am to an extent, a musician, who plays bass. I remember as a youngster playing some hoops in the university rec center with a guy, who said he was a musician. I asked him what instrument he played. He said "music, all of it". Turns out it was Ron McCurdy who has head of the jazz program at the U of Kansas. He at long last mentioned that saxophone was his performance instrument. But he wasn't "just" a sax player. That conversation stuck with me. Be a musician. To do that you need to learn music. Not just bass.
Guys like Jeff, or Patitucci, etc-- they can do what the anti-music-learning crowd can do -- groove, lock with a drummer, etc-- but they can do stuff the "I just lock with the drummer" guys/gals can't. It's true, I have played with educated musicians who weren't that great playing with feel, groove, funk, etc. So being musically literate doesn't automatically make you awesome. To be awesome, you need to be able to do it all. I know lots of really educated players who ALSO have the feel, groove, all that, too.
If I understand Jeff, he's not saying DON'T worry about groove, feel, locking, playing to the song, stage presence-- he's saying DO learn music, in all its complexity, to the best of your ability, also. It'll take more time and effort to learn to master theory than to figure out how to sneer appropriately when playing Black Sabbath, so make sure the big ticket items of education are front and center. IMO you're holding yourself back if you're afraid to try the hard work, or just don't want to put out the effort. If it's just a thing to pass the time, that's fine-- it's fun! And coming to LOVE playing music and playing bass is an important part to keeping with it. But, if you personally don't want to push yourself to be the best you could be, i'd suggest that you not say "it isn't that important" or "Jeff should not focus on the theory and hard stuff" or worse, tell Jeff he's wrong about believing the hard stuff is really important-- just becasue you don't want to.
IMO, there is no ONE thing you should do. I try (not always successfully) to do them all-- I use a metronome sometimes, to work on timing and precision-- it's helped me set an accurate internal clock. I ALSO spend time not playing, but studying, going through theory, trying chord voicings, not playing in time, but sometimes very, very slowly... I spend time with books, and have my bass in hand to try and connect the reading with my hands, not to "play" the music. I also get my time in playing gigs, where I can work on the other stuff-- artistic expression, improv, etc. Improv doesn't really go anywhere unless you know your fundamental tools-- from study.
For those who feel the need to suggest Jeff is wrong, I'd suggest going about your own plan, and not "correcting" Jeff. Those that WANT to hear Jeff's POV don't benefit from you saying "that's overrated, I don't need it". And if you don't feel you benefit from Jeff's approach, then don't pursue it. Denigrating a POV you don't personally agree with is pointless.
Just my 2 cents, from a guy that should have spent more time earlier deeply engrossed in the deep theory of music. Maybe, if I am being honest, I was afraid I couldn't hack it, at first... I found out eventually that I could, and wished I'd been more intrepid sooner.