I personally think it's unethical. And fundamentally rooted to a lack of understanding of life in general.
I rather a cat live as a cat and die as a cat than for it to live like some house furniture and then die of old age.
I had a male cat who started wanting to go outside as soon as he became a young adult and I used to let him leave, every night, sometimes he'll leave for days and come back full of scratches, hurt. He'd eat, sleep and leave again. One day he never came back. I assumed he got lost or died.
A fundamental part of being an animal is about following your instincts, and their instinct is to explore, hunt, mate and fight other males over territory.
Even if life could be risky and perilous outside, I rather the cat live the life of a cat. That's what the cat wants too. And they're also much more prepared for survival than we are.
What is accomplished when a cat is neutered, declawed, and left to live a longer life indoors deprived from its freedom ? And what is accomplished when a cat is left naturally, lived a shorter life but with all its freedom ?
Nothing much is accomplished, these things live and die for the earth. They wake up, chase after pleasure and go to sleep.
Do I have a say in this as a human ? Not really. As someone who doesn't aspire to live that kind of life, all I can do is let them live that kind of life.
And much of this is true for humans who live the life of the animal.
I actually started a thread about this in this forum back in the time when I was contemplating this issue:
if you were a petI think there is more to learn about us than it is to learn about animals when thinking about animals.
And as you can see, there is a lot more to morality than just claims like "changing the creation of Allah"