There’s the academic source, and for my anecdotal one my family’s yard in Connecticut is much quieter on a June afternoon today than it was 20 years ago.
There are responsible ways to keep indoor cats entertained. If someone can’t do that, then it seems to me they’re just as unsuited to having a pet as if they couldn’t keep it fed.
Even if you have a good point people are going to be less likely to listen to you if you start calling them lazy. This comment would be better without the last sentence
fair. projection on my part. i interpret seeing people say indoor cats lives are miserable (and using that idea uncritically to affirm their own choices) are doing so from a holier-than-thou position. to me, it's an uncreative and lazy view on pet ownership, but i getcha: flies, honey, and vinegar and all that.
Mine adores her leash walks. Cats are naturally skittish animals, being both prey and predator. So if they trust you as a source of protection the comfort of walking without worries is a benefit that outweighs the restriction of the harness. Plus it's high quality bonding time.