I live in an apartment complex with lots of animals and I see several of my neighbors leash-walk their cats regularly.

It just takes some time to train them usually. It's much easier if you get them used to it early in their lifetime, though.

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.