So there is a dirty little secret about writing, interesting, catchy, slick, sleek, or otherwise “good” basslines:
firstly, the song has to allow it
if you find yourself saying “man, I’m good at bass, and I’ve written really cool basslines before, but sometimes I just can’t find one!” The reality is that for a lot of songs- for a lot of arrangements - the best bassline is entirely unremarkable, and indeed the best call is to play roots as long notes or as a kick pattern etc etc. For an interesting bassline to emerge, first and foremost the arrangement has to allow it, to leave room for it and to have the appropriate levity and tempo and space.
When you look at players or bands, who seem to consistently have great, or at least distinctive basslines, generally their style is going to allow for it one way or another. Cake? Very polished and clean grooves just BEGGING for a good bassline. Talking Heads? Could you write music more intentionally restrained if you tried? RHCP- flea has been allowed to take the torch and run with it, and as much as there’s some dirty punky grungy looseness to the whole thing, there are parts. All the Jamerson hits? He’s typically the ONLY one getting busy, aside from maybe the singer themselves.
at the end of the day, even a very good bassist is going to have to have a very good band- or at least a very restrained band- to even allow the possibility of a particularly interesting bassline..
now of course I’m sort of implying making a busy bassline work as the topic..
As far as those little understated things, it’s almost kind of easy to trick yourself into it, and again the trick is restraint. Give yourself more space, play less notes, play less long notes, repeat more, and see what comes out. Think about the song while you’re walking around. LISTEN TO THE SINGER AND GUITARIST. LISTEN TO THE SINGER AND GUITARIST.
You’ll never write a good bassline for a song you don’t know intimately
It doesn’t get said enough, but the bass is a part time MELODY instrument. What counter melody wants to come out? Find the heart of the percussion role and if the melodic role in any song, and the good stuff is in there.