Yes, it's an important distinction, I think, and one I didn't realize until I was a senior undergrad and doing research projects. There are an awful lot of things I found really interesting to learn, but I'd never want to do for a living (General Relativity).
It's not the best idea to do an astro undergrad degree if you don't want to be an astrophysicist, but it's not a horrible plan. Anecdotally, people I know who did astro/physics degrees with me have gone on to work for R&D startups, financial companies, defence, science policy, (and other policy areas), work as geophysicists, gone on to become secondary teachers, gone to med school, and many went on to do a PhD. Quantitatively, the American Institute of Physics has a breakdown of the first jobs that astro majors get:
http://www.aip.org/sites/default/files/statistics/employment/initialempbsmsphd-a-12.pdf
A good idea if you want to go down this route is to do a double major with something that lends itself to an obvious career - engineering is a good choice.
I think that there are very few people who end up doing the job they thought they wanted to do when they were 15. I think most people actually do more "figuring it out along the way" than I did, to be honest. My biggest change after starting university was to go from wanting to be an astrophysicist to wanting to be an experimental physicist that does astro-adjacent research. :) I have a friend who changed from law and is now doing an astro PhD, even. The best you can do at 15 is set your sights on what you think you want to do now, and work hard for it. Doing lots of maths and science in high school will certainly not harm you too much, even if you decide to do english literature or computer science or art.