How do you have an attraction preference w/o turn ons/offs?

Turn-ons/turn-offs should be right next to the section in CAS where you can pick traits, likes and dislikes. If you own Lovestruck, there should be options to define what your Sim finds attractive in another Sim, like traits, colour of hair, fashion style, hobbies. 

Maybe this helps, too: https://help.ea.com/en/help/the-sims/the-sims-4/the-sims-4-gender-romance-attraction-guide/