When I first created my Apple Music Account I had an option where I choose music genres. Can I update that?

Hello!

Does not look like you can go back to that. However check out See recommended music on iPhone to see how to improve the For You section to find and suggest music you may like.

The reset option for that has been removed a few updates ago.

After initial choices for genres and artists, further refinement of your music taste is done by analyzing the music that you play, and the loves and dislikes that you give. It should get better the more you use Apple Music. Personalize Apple Music - Apple Support