It's not safety. It's more like extermination: domestic cats kill to play, not to eat. They have plenty of energy, compared to wild animals, and vets keep their life longer and more healthy. So the balance goes even more off.
(I love cats, and keep two. They have their serving of fresh air in the fire escape.)
Mine has an enclosed back verandah, a 3x15 meter space with lots of hideyholes. She also gets (supervised) time in a backyard with long grass. Doubtless she kills lizards and rodents during this time. But it's about as good a compromise as I can give her.
(I love cats, and keep two. They have their serving of fresh air in the fire escape.)