1 2
An older cat would most likely have more problems dealing with the challenges of outdoor life than a younger cat due to decreased strength, reflex speed, etc. While I was not making a statementabout ALL cats (notice I said "this cat")

OIC , I don't understand why this cat in particular should be too old , is there something medically wrong with it ? My cats were pretty lively and started slowing down about 14 but we have less dangers than the US . Usually the size of the range diminishes as the cat becomes older. Eventually they would just sit in the back garden by the door in the sun .
now that you mention it I would say that in my opinion 12 is far too old for a cat ... environment. And under 1, all the was to birth. I don't think putting animals indanger is in their best interest.

There always potential dangers in life . Life indoors is safer indoors , as it would be for anyone , but not always safe . In the OP's case this cat is at risk