As always, the response on this site is thoughtful and helpful. Really appreciate everyone's comments.
I fully expected the encouragement to play with others, play in a band, etc. Undoubtedly playing with other musicians would improve my playing. Here's the thing: I'm not young, so joining a band with young people is not in the cards. I have older acquaintances who get together to play guitar and I could join them, but their musical tastes and my musical tastes are not in line. I could live happily live the rest of my life without hearing another CCR or Lynard Skynard song, much less having to listen to them and me hack away at it. They're also into lengthy blues jams. While I fully recognize the utility of any type of live playing, the thought of blues jamming with other old men is a bit depressing (and I love the blues). Church is another possibility, but my church plays traditional hymns with an organist and a vocalist exclusively, so no bass needed there.
My work is math oriented, so music theory fascinates me, as do patterns on the fretboard. This may lead to an over emphasis on scales, modes and chord construction, but I enjoy it. When I started, I worked almost exclusively on learning and playing songs I like. I ended up being able to play the songs, and my fingering improved, but I was learning zero in the way of improvisation, hence the lessons.
My teacher is a well-known bassist in Atlanta and has a full teaching schedule. He encourages a mix of theory, exercises and song playing. He also strongly suggested playing with others, but he knows I'm not so inclined. What he has told me is that when he performs or records he's often given a key or chord progression and is expected to deliver the goods with only that direction. He's demonstrated many times how he does it, and it sure sounds musical.
All of us have different musical aspirations, and I'm the first to admit that mine are out of the mainstream. So perhaps my journey will have bigger or different bumps than most. Playing bass has given me a deeper appreciation of music and tremendous respect for the instrument and those who play well. I'm delighted when I learn a new song, or get better at any aspect of playing. Hope it keeps coming.
Thanks again for everyone's thoughts.
I was ready to jump on the bandwagon and suggest jamming with others. Actually, I still think that's sound advice. Personal anecdote:
When I first starting playing with the group of folks I'm with now, the music wasn't really my thing. We do just about all originals, and the covers we do we put our own spin on. Not sure what to call the genre we play. Folksy, eclectic with an alternative rock-ish twist? I don't know and neither does anyone else in the band really. But over time, the music grew on me, and working out my original basslines to the material has made me a better player. For context, I'm 47 years old now and have been playing bass, guitar (loosely) and keyboards since the age of 10 or so. I do record some stuff on my own as well as with this current band. Anyway, point being that you shouldn't close your mind to playing stuff you don't necessarily love. Play it anyway and you'll likely be better for the experience. When does it "click"? I have no idea honestly, but I think it's more gradual rather than a sudden thing. More context: I am not a professional musician and neither are the folks I play with. I work in a technical field myself (electrical design / drafting stuff).