It is called acting, and the television/movie industry seems to have figured it out. Of course, you do not want strangers, but rather long-standing co-workers, but this is as true for porn as it is for acting and coding.

Even if, for some reason, intimacy and passion could not be faked, you could just hire couples.

Couples have been hiring themselves for a while now :-)

A lot of couples don't mind publishing their intimate scenes for the world to see. I'd rather young people watch other people in action than professional videos which seem to have gone so plastic/mechanical/unrealistic.