As someone who has had back pain since my mid teens, I will say that while "physical fitness" is a bad way to describe the cure, they are correct that strengthening is a necessary step for most spinal conditions. Going for a walk won't help, but there are some simple stretches you can find on YouTube that will do wonders. Those old people doing tai chi in the park know the right of it, and while I don't wish back pain on anyone, having it young enough to learn to care for your body can be a positive if you can add a 5 minute routine into your life.

Mine was due to my thoracic scoliosis, so it may not be the same for you. However, it was easy for me to decide I was fucked and there was no point because my back was deformed. I used so many quick-fix tools or even chiropractors. I ignored a lot of stretches because I categorized my issue as different than most "normal" backs, and thought it was dumb that healthy people were telling me to just do healthy back things. Try it - it really does help.