It’s probably a disservice that persona development usually starts with demographics (and, unfortunately for many, ends there as well). You are spot on that more needs to be explored to create a persona/avatar that is actually helpful for your organization.
Here’s what I would recommend for everyone working to try to gain some insights into target audiences that will help fuel their growth:
Stop trying to get it “right”.
Marketing, targeting, sales, etc. are all ALWAYS in flux.
Pick a direction and go that way for a while. Pause to see how that direction feels and how it’s contributing to your goals. Adjust. Repeat.