It's easy to have idealistic views, but remember that the only reason anybody even has chickens is because they were brought in and used for food. They didn't ask to be owned. Of course. They're birds, they can't ask for anything. They are sentient, but not in the same way we are, horses are, dogs are, etc. Their brains and bodies are so different from ours that the only real comparison is that we, and they, are alive. They don't think the same as we do. They don't understand things the same way we do.
A sanctuary is a wonderful idea, but they are also very difficult and extremely costly to run. I wanted to start up a sanctuary for abused and neglected animals when I was a teenager, too. But once I was out on my own, I learned just how much animals can cost....especially unwanted ones. After all, an unwanted animal has rarely received proper care up until the point that you get it, so it's likely that its vet bills will be high. It may also have soecial needs thanks to wherever it came from. Volunteer with a rescue first, before really deciding to start a sanctuary. Get up in their ranks to see just how difficult it actually is to raise awareness and money to run a place like that.
They're amazing.....in theory....but extremely difficult to start, operate, and especially fund in practice.