To work towards aesthetic goals is completely legit. It’s not shallow and you don’t need to feel guilty about it. The important thing is to keep it in balance, don’t let the thigh gap consume you and remember its as much about how you feel as it is about how you look.
The things that your body is capable of is nothing short of incredible. Find the thing that you love, explore what your body can do, do the thing that makes you feel alive and focus on that. Once you start seeing results in your ability and you feel the excitement of your strength, technique, fitness improving, you won’t care so much about the thigh gap anyway.