Rather "risk the life of the cat, and be sure it had a good life, than make it stay indoors the rest of it's life, when it's an outdoor cat...
That's just cruel.
I know a bit about cruelty, ...and keeping an "outdoor" cat, inside hardly qualifies.
No weather, cars, kids with gasoline or firecrackers, no fights with other animals, no dogs, no poison, ...Nope, doesn't sound cruel to me. But then, I love my animals and want them healthy and long lived. I do not anthroporphize them and wish that somehow I was free and then try to live my freedom fancy through them.
There is a transition period where any animal (or person) has to adjust to a change in lifestyle, but that's life. I wouldn't let an 11 year old human run free, and most of them are cognitively higher than most cats. ...at least in my experience.
If you don't want to do it, fine. It's your animal, you'll do as you like. However don't say keeping them inside is a cruelty. That's just a lie you tell yourself to justify it.
(...and don't even get me started on the damage feral/outdoor cats do to the ecosystem! That's a whole other topic.)