I trapped and spayed/vaccinated two feral cats who had set up housekeeping in my barn and had kittens. I captured and took the kittens, kept three, all spay/neutered, and their mothers too, are still around. I provide a safe place for them and good food. It’s probably still a harder, shorter life than a domestic cat, but we do the best we can. By spaying them and releasing them back, they keep the mice down without overpopulating us with cats.
Spayed/Neutered and vaccinated feral cats released back to their local haunts also keep down the population of feral cats in general - natures way - competition for food - there is a set amount of food available in a given set of acres or vacant lots...the strong survive.
In you live in a rural or semi-rural area as I do in Texas - you will also have skunks, raccoons, armadillos, wild feral hogs, crows, ravens, turkey buzzards and even large pumas - plus a lot of coyotes eating most anything sitting still and some things moving.