I am probably not a long way down the road past you (if I am at all). I have played in a few bands for several years, and while I continue to improve, I’ve been OK at learning songs in the sets and the lines, etc., for a while. Ear training is what I’ve been working on a lot for the last 6-12 months. I’m envious of the folks who can rip out cool lines as Jimmy describes, just hearing the progression a few times. The best strategy I’ve come up with is singing as I practice scales, arpeggios, and lines in songs. For me, associating numbers and relative position is far easier (which I have to imagine is the case for anyone who doesn’t suffer from a block when the Numbers System is brought up) over trying to hear chords by name; and singing the numbers out loud is very effective for that association. I sing the key by name on the root (A, A#m, etc.) and the rest in numbers; always calling the key by name when I hit the root (any octave included). I have noticed that I pick up progressions faster and faster, but it’s hard to gauge progress. I am fortunate to have a local “anything goes” jam, which I don’t get to play every month, but I anchored as the sole bassist in December, March, and tonight, and it went really well - best yet. I was able to find the progressions, even trickier ones with the less common chords, much faster. I was about 75% on catching the whole progression by the second chorus, and I had a lot more fun with fills, connective moves, and other embellishments beyond the root/5s than I ever have in a jam. That was really affirming of the work.
And I don’t really play full chords on bass. I’ve done it on guitar or mandolin; but I don’t know that it has helped much. Hearing the chord/root is what helps my mind the most, and singing out loud is the best I’ve found for that. I used to sing in my head, but my guitarist (who has a music degree and masters in guitar instruction) convinced me to actually sing out loud. That makes a difference I don’t even understand.