I lived in flats for years and had to keep my cats indoors.
However, I took them for walks on the lead, as often as possible, which means not every day, but on average every second day.
During my parents lifetimes my cats were all happy to live indoor lives in the city, but simply loved roaming free when on holiday at my parents' house in a small village.
The pair we had when we moved to the country, adapted swiftly to country life. Ironically, the young stray who had fended for himself before being accepted here, was killed by a car. The two old cats that started life as indoor cats both died of old age.
Indoor cats need not only toys and a scratching post but a hour or so playing with their human every day. I played a form of tag with mine - we called it wild cat as they ran and chased and caught me.
When they were kittens my beloved Trold would run from one end of a fairly large flat to the other seven times without stopping, while his brother sat and watched. I never saw Storm putting his stop watch back in his waistcoat pocket, or holding it like the White Rabbit, but I am sure he was timing his brother, who wanted to grow up to be a cheetah!