How do you not develop feelings with someone who you’re just having sex with?
Your feelings are your feelings. Don’t try to downplay them.
Many people develop intensely romantic feelings towards the people they’re having sex with. Some people really like the people they’re having sex with but don’t really develop romantic feelings toward them. Some people are not at all sexually attracted to any individuals but may have romantic attachments toward them. Some people don’t like sex at all. Some people aren’t sexually attracted to individuals but might very much like the feeling of sex with the people they’re sexual with. Some people are intensely sexually/romantically attracted to certain individuals and not others.
If you think this is confusing, well … it is. Human beings are complex and don’t fit very easily into the boxes we arrange ourselves into. If you’re trying to get people to convince you not to have feelings with those you’re “just” having sex with, I would wonder why you’d want us to argue you out of your proclivities.
Maybe hookups, friends with benefits, and casual sex just aren’t your thing. Don’t force yourself to be someone you’re not.