Exactly. All cats should be indoors for their safety and that of the local wildlife
I agree, but since cats do like to be outside I came up with the best of both worlds. During the cold winters all my cats remain indoors, in the house. But in the summer when it's nice and sunny they have their own place, a huge space that is, both indoors and outdoors.

I've built them this quite lengthy playing pen, where they can run around.

Different angle. You'll see that the outdoorsy part connects to a greenhouse.

The greenhouse doubles as a chill out place, as well as the connection point from going
out to going
in. And when the kitties go inside, they have access to....

...an entire kitty cat cafe!

stocked with all kinds of yummy cat food

...and all other supplies they need.
But yeah, the main goal of this is to give them the opportunity to be outside if they want to, while still keeping them safe from external threats. Especially traffic, as I live alongside a main road. I see way too many dead animals (cats, dogs, even a raccoon once) on the side of the roads in the area to leave my cats out unguarded. And this construction keeps the birdies safe too.