Someone once brought me a baby pigeon with a badly splayed leg. Sometimes, if the bird is very young and the problem is mild - and you are experienced and knowledgeable - you can remedy this. But often, you can’t.
This one needed amputation, so I took it to a vet. I wouldn’t have had the tools and resources to remove the leg under anesthesia and understand everything involved in recovery.
As you seem to understand, my argument is with people who get all ‘touchy-feely’ when they see a suffering animal, and think they can somehow ‘help’ it, when what the animal needs is immediate professional care.
In most areas, any vet can put you immediately in touch with someone who can help. They know all the rehab resources, because people often contact them about wildlife, or even bring the animals to them.
That’s great, thanks!