You can keep them safe and happy inside though. Also, you can train them to walk on a leash -- it isn't easy, but perfectly doable. My cat enjoys her brief supervised forays into the back yard or basking on the balcony in the sun.

Many cats are perfectly suited to be indoor cats, it really does depend.

Anecdotal: I have a feral rescue who they told me couldn't be rehabilitated into an indoor cat, but after a month of being exclusively indoors (unintentionally, I had to move out of my house for mold treatment), his anxiety was almost completely gone and he started being friendly and affectionate to everyone who gave him attention.

I think most people are missing how much a cat can get out of being in its natural environment, it should be intuitively obvious how important it is to them if you've lived with cats that do and don't have access to that and see how much they value being able to do cat things outside and basically have their own lives independent from their owners.