TNR is the worst policy ever. We had a colony around the office I used to work at. The people in the office across the street would feed them. Then that office went out of business; no one to feed the cats. Then someone started showing up, she’d drive up, put piles of cat food in the middle of the parking lot and sidewalks and leave. My boss confronted her one day and she told him they were TNRed. He showed her the fleas that were jumping on and off of him just from walking through the parking lot. The front door area smelled like fresh cat spray every morning. Sometimes adults need to make difficult decisions.
We were having a problem with cats in our neighborhood. It started after the housing crash and I think cats were dumped after foreclosure, but we also had some that were definitely feral. I paid for two female spays (kittens) and took over the care of those two. It was only $25 each, but I had to do the trapping. Another neighbor took care over a sweet gray boy who was obviously dumped. The key is to only put out enough food for the animal you are caring for (and which has been fixed) and don't let the food sit out there all day to attract others. We had another neighbor who was setting out a huge tray of food and started attracting more. HOA fined her, she stopped feeding, we stopped getting new ones.