Cats, like dogs, can be easily trained. It is all about finding the proper motivator for your specific cat. What can you give your cat that will reinforce that behavior, or cause that behavior to increase in frequency? Some cats may be very motivated by food while others may be more motivated by play, praise or physical attention. In my house, Cecilia is motivated by food (especially cooked chicken and hard food treats) and play while Macy is motivated more by praise and attention.
In order to determine what motivates your cat consider their personality. Is your cat extremely affectionate? If so, try reinforcing behaviors with praise and petting. Is your cat high energy? If so, try reinforcing behavior with short bouts of play. Does your cat often break into bags and steal treats? If so, try reinforcing with their favorite foods. Considering what your cat enjoys will help you understand what motivates them. Often new trainers focus too much on reinforcing behaviors with food treats, but some cats can be picky about food and many cats seem to be more motivated by activity, such as play.
In fact, while I was leading a recent kitten clicker training class we found (after a personality assessment) that 75% of the kittens were more motivated by play than by food. Next time you have issues training your kitty with treats try reinforcing with short bouts of play or petting instead.
maueyes 
With most rescues from feral colonies food works just fine. I had a shy cat who I taught to endure my proximity and caressing her by handing out treats. And my FunTom (from a farm) learned the word “Sit” that way. Both had to learn first that human company in itself can be fun. Even today their tail goes flicking when I caress them – a sure sign that they are not sure about it. Two conflicting emotions. And I got the tom for over 9 years now. Cats who are brought up with humans around are different, I get that. But the shy, half-feral variety usually answers best to food.
Hi! This idea really goes back to the personality of the cat. Cat personality is in part shaped by the experiences it has during it’s lifetime (in addition to genetic factors). So, as you say- food often works well with unsocialized/shy cats. This would make sense since these cats have little experience interacting with humans and therefore would most likely not find human attention or play reinforcing. But, I have worked with extremely shy cats that only came out of their shell by using play and praise. So it is really about the cat and what that individual enjoys because even within groups of cats individual variation is really diverse. Thanks for the comment!
Elena and Linnea both seem motived by play and affection. Neither like treats. I haven’t worked with Linnea yet and need to go back to working with Elena. She knows up now.