All my cats have stayed indoors. I've lived in suburbia or cities where there are too many cars or neighbors who don't like cats and now coyotes where I'm living. They've always been fine indoors and lived long lives.
I would also not let them outside, the roads today are not the roads of 10 or 20 years ago! Sadly, I have lost too many of my farm cats to the roads. And then it depends on each cat. My Henry is so happy to be indoor only, but Max woud just love to be able to be outside, although this is impossible living in the middle of Madrid....
I don‘t think that it is more dangerous than 10 or 20 years before but the nighbours have lost two cats on the main road the last three years and the three cats they have now walk down the hill to the road, too and cross the road, I have seen them there and that is of course very dangerous. My old gang never walkend down the hill, their territorry was the big field behind the house but you never know what these four will do.....Well, and now that I am alone, my husband and my mother passed away last year, then no one would be here to keep an eye on them when I have to leave the house and they are out. And although I am not a fraidy-cat....we left the balcony door open day and night for the cats, I think I wouldn‘t do that now but with this enclosure there would be no chance for someone to get into the house over the balcony and I can leave the door open. It‘s of course a bit sad for the cats , the life of an outdoor cat is more interesting and thrilling but they don‘t miss it, I am sure they have forgotten the few weeks they lived on a farm because they were very young when I got them.