There is a very essential difference between "domesticated" and "tame".
An animal that is "domesticated" was intentionally bred by humans over many generations to ensure a safe food supply that doesn't rely on hunting or to exploit other characteristics (like rodent control by cats). This process takes many generations bred in captivity.
An animal is "tame" when it doesn't shy away from human contact. Both domesticated and wild animals can be tame or feral or something in between. Most animals aren't born tame, they need to get used to human contact. This works best if the animal has contact to humans from birth or from a very young age, a process called "socialization". Some species can become tame later in their life, but I think the majority of animals cannot become tame after their period of socialization ended.
This guide to pigeons includes:
Handle your pigeon. Talk to him and touch him gently and allow him to get used to you and your voice. Giving him attention will make him more likely to be a lifelong buddy. Ignoring him in a cage will only isolate him. How often how well he was handled while he was at the breeders will also influence how easily adaptive he might be. A well socialized pigeon has been handled by numerous people during his squab stages. Otherwise you might have to take a very gentle and patient approach.
So the reasons why the dove you cared for didn't become tamed in 3 months are probably:
- It wasn't socialized with humans at a young age
- You didn't spend much time with it other than offering food
- It may have had negative experiences with humans in the path that scared or hurt it. Although you are a different person, this dove had no reason to trust you.
Please don't be heartbroken. This was a wild bird that would probably never become tame the way you'd want.